Meeting of the SIL Plankton Ecology Group (PEG 2012) · Abstracts of the SIL Plankton Ecology Group. Mexico City, Mexico,12-18 February, 2012 _____ 2 Vertical flux of phytoplankton

Meeting of the SIL Plankton Ecology Group

(PEG 2012)

February 12-18, 2012, Mexico City, Mexico

Book of Abstracts

Book of Abstracts

The Organizing Committee

Brian Moss (UK) H.J. Dumont (Belgium) L. DeSenerpont Domis (The Netherlands) Miquel Lürling (The Netherlands) R.D. Gulati (The Netherlands) S. Nandini (Mexico) S.S.S. Sarma (Mexico) Z.M. Gliwicz (Poland)

Abstracts of Presentations

Invited talks, oral and poster presentations

Abstracts of the SIL Plankton Ecology Group. Mexico City, Mexico,12-18 February, 2012 _________________________________________________________

1

Relation between microcystin-LR concentration and the potentially toxic cyanobateria in Valle de Bravo reservoir, Mexico State

Alillo-Sánchez José Luis, Gaytán-Herrera Martha Leticia, Martínez-

Almeida Victor Manuel and Ramírez-García Pedro

Research and Postgraduate Division (UIICSE-CyMA Project), Universidad Nacional Autónoma de Mexico/FES-Iztacala, Avenida de los Barrios No. 1, 54090 Tlalnepantla,

Estado de México, Mexico. [email protected] or [email protected] The presence of cyanobacterial blooms is a characteristic of eutrophic inland waterbodies. Some taxa produce toxins that are released to the environment. These include the so-called microcystins, which have hepatotoxic and dermatological effects on animals and humans. Valle de Bravo reservoir (Mexico State) is the main source of water for the Cutzamala system, which supplies drinking water to the west of Mexico City and conurbation areas of Mexico State. Monthly surface water samples were analyzed for physico-chemical parameters and cyanobacteria species richness and abundance at five stations from February to November 2010. We also measured the concentration of microcystin-LR using a commercial kit (EnviroLogixTM) based on ELISA assay. The results indicate the eutrophic condition of the reservoir. Of the 19 taxa of cyanobacteria found, Pseudanabaena wesenbergii and Microcystis mucicola, were the most frequent and abundant species. From February to June microcystin concentration exceeded the maximum guide value for drinking water sources established by WHO (1 g / L). The highest value (5.56 μg / L) was recorded in April. The concentration of microcystin was related with the biovolume reached by species of order Nostocales, especially Anabaena planctonica (r = 0.901, n=50). We suggest continuous monitoring of water quality in this reservoir and to alert users who practice the various recreational activities.


2

Vertical flux of phytoplankton in a tropical, oligotrophic Mexican Lake

Ardiles Vilma1, Alcocer Javier2 and Oseguera Luis A.2

1Programa de Posgrado en Ciencias del Mar y Limnología, UNAM..A.P, 70-305. Colonia Universidad Nacional Autónoma de México. 04510. Delegación Coyoacán.

México, D.F. e-mail: [email protected] 2Facultad de Estudios Superiores Iztacala, UNAM. Proyecto de Investigación en

Limnología Tropical. Av. de los Barrios No.1, Los Reyes Iztacala, Tlalnepantla, Estado de México 54090 México.

Alchichica is a tropical, oligotrophic lake whose phytoplankton biomass is dominated by large size phytoplankton (i.e., diatoms and cyanobacteria). The fast sinking phytoplankton leads to carbon and other nutrient exportation out of the productive zone of the lake. The aim of the present study was to identify and measure the sedimentation fluxes of the phytoplankton species and their temporal dynamics along three years (June 2006 to June 2009) to better understand the magnitude of nutrient fluxes associated to the different dominant taxa. The phytoplankton fluxes were highest at the onset of the stratification, just after the winter diatom bloom. Phytoplankton fluxes varied between 8.5 x 106 and 1,159 x 106 cells m-2 d-1 during the circulation period and between 2.0 x 106 and 1,878 x 106 cells m-2 d-1 along the stratification. The main settling phytoplankton groups were diatoms, cyanobacteria and chlorophytes. From June 2006 to December 2008 the diatom Cyclotella alchichicana was the most important species found in the traps constituting up to 98%. However, from January to June 2009, Cyclotella choctawhatcheeana (33-70%) and Chaetoceros elmorei (0-57%) replaced C. alchichicana as the dominant species. Key words: phytoplankton flux, tropical lake, oligotrophic lake


3

The physical and chemical behavior and phytoplankton biomass of an artificial aquatic system in Cozumel, Mexico

Arroyo Castro Jovana, Cervantes Martínez Adrian and Medina Palomo Carolina

Universidad de Quintana Roo, Unidad Académica Cozumel, Depto. Ciencias y

Humanidades; Cozumel, Quintana Roo, 77600. [email protected] The following study describes the physical, chemical variables and the dynamics phytoplankton biomass (chlorophyll a) in an artificial aquatic system located in Cozumel, Mexico (N 20 29 '18.3" W 86° 56' 22.8"). This study considers two climatic periods (the rainy and winter storm season). Based on the physical and chemical analysis of the water, the system exhibited the following characteristics: warm tropical water (24.8± 1.9°C), low conductivity (389.6 ± 75.84 S/cm), freshwater (salinity= 0.2 ± 0 mg/l), poorly oxygenated (1.1 ± 0.3 mg/l) and saturated (7.7 ± 2.7%). Based on the biomass of phytoplankton the system can be classified as mesotrophic (5.2 ± 3.8mg/m3). It is important to mention that the concentration of the phytoplankton increased as the cold season neared, due to the probable decrease in the abundance of possible primary consumers that live in this system. Investigations of artificial systems allow us to understand the relationship between the phytoplankton biomass and dynamics, and physical and chemical behaviors of aquatic systems. Keywords: Biomass, Limnology, mesotrophy


4

The light-dark bottle method: an option for the study of oxygen consumption of zooplankton in situ

Benítez-Díaz Mirón Marcela Ivonne, Garza-Mouriño Gabriela and Castellanos-Páez María Elena

Laboratorio de Rotiferología y Biología Molecular de Plancton. Universidad Autónoma Metropolitana. Calzada del Hueso 1100. Colonia Villa Quietud, Delegación Coyoacán.

México, D. F. C.P. 04960. [email protected] There are various studies that explain the behavior of rotifers in low dissolved oxygen concentration; however, the knowledge about their oxygen consumption in the natural environment is very scarce. The purpose of this study was to quantify the in situ oxygen consumption of the planktonic fraction <50 m and the zooplankton fraction between 50-220 m. Six incubations were performed monthly during 2011. They were done in triplicate in sterile transparent and amber glass bottles of 4-liter of capacity. The zooplankton was concentrated 20 times and was starved for 45 minutes in water pre-filtered through 0.22 m, and then the incubations of 40 minutes were done in water pre-filtered through 50 m. The final oxygen content was determined by the method of Winkler. The initial oxygen values observed ranged from 3.18 to 9.45 mg.O2.L-1. Our results show that the oxygen consumption of the zooplankton community of less than 50 μm was between 0.075 and 0.53 mg.O2.L-1, while the larger community of 50 m consumed from 0.28 to 1.51 mg.O2.L-1. The lower density was 35.58 ind. mL-1 and the higher density was 1900.00 ind.mL-1. Finally, in terms of fixed carbon was found that in the experimental conditions [20x], the zooplankton can fix from 196.76 to 1045.95 mgC.m-3.h-1. Key words: zooplankton, oxygen consumption, light and dark bottles method.


5

Morphometric characterization of Staurastrum gracile Ralfs (Chlorophyta) from tropical reservoirs in Mexico

Calderón Eva1 and Tavera Rosaluz2

1 Posgrado en Ciencias Biológicas, Facultad de Ciencias, UNAM.

2 Departamento de Ecología y Recursos Naturales, Facultad de Ciencias, UNAM Apartado Postal 70-747 CU Coyoacán, México DF. Email: [email protected] Morphometry of Staurastrum gracile was studied using in situ samples and isolations in pure cultures, with material collected on the shallow shores of reservoirs of the State of Mexico (Valle de Bravo and Taxhimay). We have documented in natural conditions as well as in the artificial, pleomorphic limits of this species (morphological variability that is part of life cycle) and polymorphism (morphological variability associated with environmental conditions). The documentation refers to a comparison of characters compiled from the literature, observed in situ and observed experimentally by modifying various conditions of pH and nutrient concentrations, which are some of the factors that desmids respond with great sensitivity. The population variability analysis based on morphometric tools, has helped to address critically the morphological overlap between varieties of S. gracile and between it and other species of Staurastrum. Based on the results, we question the validity of Staurastrum gracile var. nanum and Staurastrum paradoxum and suggest that geographical variation in S. gracile in Mexico corresponds to ecotypes associated with environmental conditions.


6

Vertical migration of six rotifer species of the Brachionidae family in the Cuemanco Channel, Xochimilco

Castellanos-Páez María Elena, Contreras Tapia Rubén Alonso, Garza-

Mouriño Gabriela, Zamora García Margarita, Benítez Díaz-Mirón Marcela Ivonne & Vázquez Romero María del Carmen

Laboratorio de Rotiferología y Biología Molecular de Plancton. Universidad Autónoma Metropolitana. Calzada del Hueso 1100. Colonia Villa Quietud, Delegación Coyoacán.

México, D. F. C.P. 04960. [email protected] The pattern of vertical migration over a 24-hour cycle of six rotifer species was analyzed. The studied species were the dominant ones: Keratella tropica, Brachionus budapestinensis, B. angularis, B. calyciflorus, K. cochlearis and B. quadridentatus. The temperature, oxygen, ammonium, nitrite, nitrate, total phosphorous and chlorophylls, were evaluated, and the canonical correspondence analysis was done in order to determine the relations between the species and the physicochemical parameters. The six studied species showed a similar migration pattern with a movement to the surface at night. Asplanchna brightwellii has a correlation with three of the six species; B. calyciflorus (r=0.52), B. budapestinensis (r=0.66) and B. quadridentatus (r=0.55). Brachionus calyciflorus showed an inverse significative correlation with the chlorophyll a (r=-0.50), the same as K. cochlearis (r=-0.57). B. budapestinensis had a correlation with ammonium (r=0.61) and an inverse correlation with dissolved oxygen (r=-0.55). B. quadridentatus had an inverse correlation with the pH (r=-0.56). The other variables did not have any significative correlation with the species. Keywords: rotifers, Brachionidae, migration, Xochimilco, canonical correspondence analysis.


7

Zooplankton ecology and limnology of two dissolution lakes in the Yucatan Peninsula (Mexico)

Cervantes-Martínez Adrián and Gutiérrez-Aguirre Martha Angélica

Universidad de Quintana Roo, Unidad Académica Cozumel, Depto. Ciencias y Humanidades; Cozumel, Quintana Roo, 77600. [email protected]

In two dissolution lakes in the eastern portion of the Yucatan Peninsula, Mexico, the effect of biotic and abiotic variables on the spatio-temporal structure (abundance, diversity, distribution, and richness) of the limnetic zooplankton was surveyed. The study comprised of one annual cycle (2003- 2004) with monthly sampling. A limnological characterization of the two systems is proposed, considering the mixing and stratification patterns, physical and chemical variables, and the trophic state on the basis of chlorophyll (mg/ m3) concentration. The statistical differences in most of the environmental variables considered here, provided evidence to support the hypothesis that these tropical systems are not homogenous on both temporal and spatial scales, in spite of their little temperature oscillations. According to the indicators “El Padre” (EP) can be considered as a meso-eutrophic system, whereas the “Minicenote” (M) is oligotrophic, both systems are warm monomictic lakes. The limnetic zooplankton was more abundant in the rainy and dry seasons in both lakes. The most abundant species in EP was the rotifer Keratella americana, whereas in the M the calanoid copepod Mastigodiaptomus nesus was dominant. Temporal and spatial oscillations of the zooplankton abundance in P were related to the Chaoborus predation and anoxia in the bottom, whereas in M these were related with the algal biomass. The Shannon-Weaver index was inversely related with the eutrophication indicators in the meso-eutrophic system, and no correlation between the diversity index and the independent variables considered here was found in the oligotrophic system suggesting that in the lake, other mechanisms other than those dominated by the predation or the energy translation through trophic levels are acting in the diversity regulation in this oligotrophic system. A PCoA analysis shows that the populations of individual species of zooplankton in these lakes appear to occupy separate niches in resource spaces. Keywords: nutrients, dissolution lakes, chlorophyll , stratification.


8

A review on the effects of ultraviolet radiation on aquatic communities

Chaparro-Herrera Diego de Jesus1, Esmeralda Bravo-Hernández2,

Brenda Karen González Pérez3, Valencia Vargas Meetztli Alejandra3,Nandini S.3 and Sarma S.S.S.3

1Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México

2Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México

3Laboratory of Aquatic Zoology, Division of Research and Post-graduate Studies, National Autonomous University of Mexico Campus-Iztacala, Av. de Los Barrios #

1, Los Reyes, Iztacala, Tlalnepantla, State of Mexico, Mexico.

The intensity of ultraviolet radiation in the valley of Mexico is often very high, with the UV index ranging from 8 to11. Although these rays are not visible, their adverse effects on aquatic communities have been well established. Several studies show that, both, the physiology (survival, growth and reproduction) and the behaviour (vertical migration) of zooplankton are affected due to an increase in the intensity of UV radiation. Here we present our findings based on literature survey from the studies focusing on the effect of UV rays on zooplankton which were conducted over the past 15 years. We found that USA and China are the countries that have the most published articles (four per year) on the effect of UV rays on terrestrial and aquatic communities. Of all the studies on UV radiations 20 to 30% studies have considered the UV effects on aquatic systems. In Mexico, only 13% of articles published on the effects of UV radiation were on aquatic systems. Worldwide, in aquatic systems, the effect of UV radiation has been studied mostly on fish, Daphnia and calanoid copepods. In addition to our literature survey, we also present a prototype of an apparatus we designed to study the migration of zooplankton faced with fish predation pressure and the adverse effects of UV radiation in shallow lakes in Mexico. Keywords: UV radiation, Zooplankton, Vertical migration, Predation, Defense mechanisms.


9

Dispersion, local adaptation and insularity as determinants of zooplankton diversity patterns in Cuenca Oriental lakes, Mexico

Ciros-Pérez J.1, Ortega-Mayagoitia E.1, Alcántara-Rodríguez J.A.2,Barrera-Moreno O.A.3, Lomelí-Ramírez N.A.4, Serrania-Soto C.R.2, López-

López B.5 y Piedra-Ibarra E.6

1Investigación en Limnología Tropical, FES Iztacala, UNAM. 314, 54090 Tlalnepantla, Edo de México.

2Posgrado en Ciencias Biológicas, FES Iztacala, UNAM. AP 314, 54090 Tlalnepantla, Edo de México.

3Posgrado en Ciencias del Mar y Limnología, FES Iztacala, UNAM. 4Carrera de Biología, FES Iztacala, UNAM.AP 314, 54090 Tlalnepantla, Edo de

México. 5Carrera de Hidrobiología, UAM-Iztapalapa

6Laboratorio de Fisiología Vegetal, UBIPRO, FES Iztacala, UNAM. AP 314, 54090 Tlalnepantla, Edo de México.

Cuenca Oriental is a water basin located in Central Mexico (Tlaxcala, Puebla and Veracruz States) characterized for having eight endorheic lakes, very close one to each other (<40 km), with island-like distribution, and with similar geologic age (Late Pleistocene), but with contrasting ecological conditions: deep vs. shallow, perennial vs. ephemeral, oligotrophic vs. eutrophic, with or without fish, and salinities that range from 0.4 to 11 g L-1; thus, this lacustrine system constitutes an ideal model for the study of ecological and evolutive processes in zooplankton organisms. With this aim, we analyzed: (1) the zooplankton species richness, (2) the effect of salinity on both the hatching patterns of resistance structures from sediments and (3) on the fitness of representative populations of rotifers and copepods, and (4) the potential gene flow (intra and interpopulation reproduction) among parapatric populations. In addition, (5) we evaluated the divergence of the COI gene among these representative populations. We found that: (1) the regional biodiversity is relatively high, each lake having a distinct specific composition and few shared species. (2) There are differences in the hatching patters of resistance structures and in the fitness of populations due to the different salinities, also, adaptation to local conditions in several rotifer and copepod populations was observed. (3) The genetic divergence among populations of rotifers (Brachionus group plicatilis) and copepods (Leptodiaptomus cf. sicilis) was relatively low (K2P<1%), however, the distribution pattern of haplotypes of copepod populations reveal the persistence of founder events and a low rate of genetic flow in natural conditions. In spite of the close location of lakes and the possibility of genetic flow by means of resistance structures, both isolation and environmental heterogeneity had promoted complex diversity patterns in the zooplankton of Cuenca Oriental lakes.


10

Prevalence of pelagic route in Lake Patzcuaro (Mexico)

Córdova Tapia Fernando and Zambrano Luis

Laboratorio de Restauración Ecológica, Instituto de Biología, UNAM C.U., Mexico City, Mexico. Twt@ZambranoAxolote

Lake Patzcuaro represents one of the most important freshwater fishing areas in the country. However, fish production in this lake has declined due to degradation of water quality, overfishing and the introduction of exotic species. The southern part of the lake has the highest values of human settlements, tourists, municipal discharges, density of exotic species and the rate of sedimentation. One of the first steps in determining how an ecosystem is affected is to characterize its trophic interactions. We used stable isotope analysis of carbon and nitrogen to understand the trophic dynamics of the lake and its relation to land use and environmental conditions. Significant differences were observed in the isotopic signatures between different regions of the lake. The southern zone presented only a pelagic food web based on phytoplankton, while the central and northern regions presented benthic and pelagic species. The trophic niche analysis suggested that the southern region had a lower trophic diversity, while the central area had the highest diversity. Environmental conditions in the southern zone of the lake resulted in the loss of an entire trophic route, which thus threatens the stability of the trophic structure and the native fish populations.


11

Light stress: A possible factor affecting Microcystis aeruginosastrains?

Deblois Charles P., Xu Kui and Juneau Philippe

Department of Biological Sciences-TOXEN, Ecotoxicology of Aquatic Microorganisms

Laboratory, Université du Québec à Montréal, Montréal, Canada Blooms of Microcystis aeruginosa occur frequently in many freshwater ecosystems worldwide, but the role of environmental factors in promoting the growth and determining the proportion of toxic and non-toxic strains still require more investigation. In this study, two toxic and two non-toxic strains (CPCC299 & FACHB905 and CPCC632 & FACHB315) were exposed to high light (HL) condition, similar to light intensity found at the surface of a bloom, in order to evaluate their sensitivity to photoinhibition. We also estimated their capacity to recover from this HL stress. For all strains, our results showed higher photosynthetic activity inhibition with HL treatment time. When comparing the extent of photoinhibition between strains, both toxic strains were more resistant to the treatment and recovered completely after 3 hours, while non-toxic strains needed more time to recover. For toxic strains, rETR under HL was higher compared to the rETR under LL control condition despite 50% photoinhibition. This suggests that the detrimental effect of HL (up to 2hr) is outweighed by their higher photosynthetic potential. This conclusion did not stand for non-toxic strains and indicates their preference for LL environment. It appears that the toxic strains have developed different mechanisms to cope with high light intensity than non-toxic strains. Indeed, toxic strains have an energy dissipation pathway related to the non-photochemical quenching that is not found in non-toxic strains. We also demonstrated that LL/HL cycle induced a 259 % increase in cell yield for a toxic strain and a 22% decrease for a non-toxic strain. This also indicates that toxic strains have higher tolerance to HL in fluctuating light environment. Our data demonstrated that differences of sensitivity to HL between strains can modify the competitive outcome between toxic and non-toxic strains and may affect bloom toxicity.


12

Pelagic flatworm predation: different sensitivity of Daphnia galeataand Ceriodaphnia quadrangula to Rhynchomesostoma toxins, and

auto-intoxication and self-castration of Mesostoma ehrenbergi

Dumont Henri J.1, Han Bo-Ping1 and Rietzler Arnola C.2

1Hydrobiology Institute, Jinan Uinversity, Guangzhou, China 2Department of Biology, University of Belo Horizonte, Brazil.

Following a reduction in fish populations in 2004–2005, a new, single annual pulse of pelagic flatworms (Rhynchomesostoma sp.) was observed in early summer during 2006–2009 in Liuxihe, a freshwater reservoir in South China. As soon as these worms appear, Daphnia galeata retreats into dormancy, one month earlier (July) in the presence of flatworms than previously observed (August) with fish, while the population of the related Ceriodaphnia quadrangular tends to increase. We show, through in situ lake sampling, in large enclosures and by laboratory observations, that Ceriodaphnia, although perhaps competitively inferior in its ability to acquire algal food, has a higher tolerance to flatworm exotoxins. As a result, Ceriodaphnia manages to coexist with and proliferate in the presence of the flatworm. Observations in the laboratory suggest that the flatworm population autoregulates by being sensitive to its own toxins and that Ceriodaphnia, even if prey to the worms, likely incurs more benefit than cost from their presence. The toxins of another, larger flatworm (Mesostoma ehrenbergii) are experimentally shown to be also a factor in population regulation: a form of auto-castration is recorded that appears to be worm density-dependent.


13

Direct and indirect effect of allelochemicals of Hydrilla verticillata on the life table Simocephalus spp. (Crustacea: Cladocera)

Espinosa-Rodríguez Cristian Alberto1, Rivera de la Parra Ligia2, Martínez-Téllez Aurora2, Gómez-Cabral Gisela Carmen1, Sarma S.S.S.2 and Nandini

S.2 2Laboratory of Aquatic Zoology, Division of Research and Postgraduate Studies, UMF Building, National Autonomous University of Mexico, Campus Iztacala, A. P.314, CP

54090, Tlalnepantla, Estado de Mexico, Mexico. The submerged macrophyte Hydrilla verticillata has an antagonistic relation with cyanobacteria through the release of allelochemicals. However, the effect of these allelochemicals on other planktonic species has not been well-studied. We compared the effect of natural plant, artificial plant and allelochemicals from Hydrilla- conditioned medium with controls on the specific growth rate (μ) of Scenedesmus acutus during the exponential phase. In addition, we also evaluated the effect of Hydrilla-allelochemicals on the demography of the cladoceran zooplankton Simocephalus spp. using standard cohort life table method. In presence of artificial plants, the growth rates of Scenedesmus were significantly lower (μ=0.472) as compared to controls (μ=0.883). The presence of macrophyte-conditioned medium did not significantly affect the algal grow rates (μ =0.836), while the presence of natural (living) plants caused a significant decrease of this variable (μ=0.407). The Hydrilla-conditioned medium had a stimulatory effect on both the survivorship and the reproductive variables of Simocephalus spp.; as compared to controls, the fecundity was almost 3 times higher while the longevity was about 40 % longer. Our results tend to suggest that since the Hydrilla-allelochemicals enhanced the reproduction and the longevity of Simocephalus, this could lead to a more competitive pressure on other cladoceran species with similar foraging strategies and thus bringing a change in the trophic dynamics in a given aquatic ecosystem. Keywords: Allelopathy, Scenedesmus acutus, cladocerans, macrophytes.


14

Horizontal migration of zooplankton in a shallow, high-altitude reservoir (Isidro Fabela, Mexico)

Fernandez Rocío1,3, Aguilar-Acosta Claudia Romina2, Figueroa-Sánchez, Michael Anai3, Gayosso-Morales Manuel Aaron3, Zamora-Barrios Cesar

Alejandro3, Nandini S.3 and Sarma S.S.S.3

1Doctorado en Ciencias Biológicas, Universidad Autónoma Metropolitana. 2Posgrado en Ciencias el Mar y Limnología, National Autonomous University of

Mexico, Ciudad Universitaria, Av. Universidad 3000, CP 04510, Mexico City, Mexico. 3Laboratory of Aquatic Zoology, Division of Research and Post-graduate Studies,

National Autonomous University of Mexico Campus-Iztacala, Av. de Los Barrios # 1, Los Reyes, Iztacala, Tlalnepantla, State of Mexico, Mexico.

It is well established that zooplankton undergo horizontal and vertical migrations in freshwater ecosystems. Among the main factors that induce this behaviour are the presence of vertebrate and invertebrate predators and light. Here we studied this phenomena in a shallow (< 2 m), oligo-mesotrophic, high altitude (3300 msl) reservoir in the State of Mexico. At the time of our study the water temperature ranged from 10-12°C, the chlorophyll concentration was around 2.0 μg L-1and the oxygen levels were between 6-8 mg L-1. The reservoir has a fairly high density of trouts (Oncorhynchus sp.). The benthic and littoral zones were covered with the macrophyte Hydrilla sp. and the chlorophyte Spirogyra sp. Observations were made in November. Samples were collected at six points, separated by 5 meters, from the shore to the pelagic zone. Plankton samples were collected at 0400, 0600, 0800, 1600, 1800, and 2000h. Twenty liters of water from each of the 3 depths, 0.5, 1.0 and 1.5 m, were filtered using a 50μm mesh and a pooled simple was collected. Of the eight species of cladocerans and 18 species of rotifers observed in this study, Daphnia laevis, Chydorus brevilabris and Trichocerca similis showed the maximum horizontal movement. Copepods were the most dominant of the three zooplankton groups analysed; the nauplii were more dominant at the shore in the early morning hours and between 10 to 25 m from the shore in the afternoon.


15

Effect of temperature level and oscillation on some life history parameters and fatty acid profiles of Moina macrocopa (Cladocera) Gama-Flores José Luis1, Huidobro-Salas María Elena1 and Sarma S.S.S.2

1Carrera de Biología, National Autonomous University of Mexico Campus-Iztacala, Av. de Los Barrios # 1, Los Reyes, Iztacala, Tlalnepantla, State of Mexico, Mexico.


1, Los Reyes, Iztacala, Tlalnepantla, State of Mexico, Mexico. Species of Moina are largely adapted to high temperatures. In tropics, Moina is usually cultured at or above 25°C as diet in aquaculture. Temperature is one of the important environmental factors affecting the survival and reproduction of all organisms. Global warming affects the distribution of zooplankton including cladocerans. In theory, the increase in temperature can be dangerous because of its effect metabolism of individuals. However, while evaluating the effect of temperature on planktonic organisms, the test species are usually cultured at fixed temperature intervals. In nature, rarely temperature remains constant within a 24 h cycle. Therefore, tests involving variable temperature intervals may reveal population growth trends which are different from those at fixed temperatures along with the fatty acid evaluation in the individuals. In high altitude waterbodies of Central Mexico the magnitude of temperature oscillations within a 24 h cycle ranges between 15 and 30°C, posing zooplankton to a higher thermal stress. One important group of lipids is the fatty acids which are not only structural components of the cell membranes but also respond to thermal variation. In this work we evaluated the effect of variable temperatures (12h at 20°C, transferred at every 6 h intervals to 25°C and 30°C) at fixed food (Chlorella vulgaris) level (0.5X106 cells ml-1) on the population growth and demography of Moina macrocopa. To compare these data, tests were also conducted at these fixed temperatures. Population growth data showed significant differences of M. macrocopa under variable temperatures as compared to those cultured at fixed temperatures. In general, M. macrocopa cultured under variable temperatures had higher population abundances and growth rates as compared to those at fixed temperatures. There were also significant changes in the demographic variables of M. macrocopa depending on the intensity of temperature and the mode of exposure. M. macrocopa showed optimal growth at 25°C. The temperature-directed effects were reflected also reflected in the fatty acid profiles of M. macrocopa.


16

Intraspecific differences in the demography of Asplanchna girodi(Rotifera) in relation to temperature regimes

García-García Gerardo1, Jiménez-Contreras Jorge2, Moreno-Gutierrez Rosa Martha1, Nandini S.1 and Sarma S.S.S.1


1, Los Reyes, Iztacala, Tlalnepantla, State of Mexico, Mexico. 2Postgraduate Programme in Limnology and Marine Sciences, National

Autonomous University of Mexico, Ciudad Universitaria, Av. Universidad 3000, CP 04510, Mexico City, Mexico. [email protected]

We studied the intra-specific differences in the response of rotifers to temperature ranging from 20° to 30°C. We hypothesized that organisms from different environments may present genotypic and phenotypic differences, as a result of selection which would lead to differences in their capabilities to resist a wide range of environmental variables including temperature. To test the aforementioned, we exposed six clones of the predatory rotifer Asplanchna girodi to three temperatures (20, 25 and 30°C) with 8 eight replicates per clone (in all 144 test jars). Test species was separately collected from Lake Zempoala (Z) (State of Morelos) and Lake Xochimilco (X) (Mexico City)), both these locations were separated by a mountain system with a maximum elevation of 3900 m a.s.l. From each waterbody five individuals were isolated and separately cultured to establish clonal cultures. Each test jar received one individual of a clone of A. girodi from a known locality. Each jar contained 25 mL of medium (semi-hard reconstituted water), 100 ind mL-1 of another rotifer Anuraeopsis fissa as prey and with Chlorella vulgaris at a density of in 0.5X106 cells mL-1. The medium and prey were changed daily, and offspring if produced were counted and eliminated. The experiment was terminated when the test individual had died. The patterns of survivorship and demography showed significant inter-clonal differences. The inter-clonal variation was less evident at 25° and 30° as compared to 20°C. At 20ºC the population growth rates per day (r) of A. girodi from three Zempoala clones were significantly different: 0.72-0.79 (Z1), 0.86-0.91 (Z2) and 0.74-0.82 (Z3). The growth rates of the predator from Xochimilco clones at 20°C ranged from 0.78-0.85 (X1), 0.81-0.98 (X2) and 0.81-0.83 (X3). We also found significant differences in the growth rates of Asplanchna from Xochimilco clone at 20°C (r= 0.98) and 25ºC (r= 0.87), and in the Zempoala clone at 30ºC (r= 1.43). Our study shows that not all clones were capable of adapting to the temperatures tested; it is therefore important to consider inter-clonal variability in Asplanchna girodi in routine bioassays.


17

Evidence of cryptic speciation in some common rotifers (Rotifera) of Mexico

García Morales Alma Estrella and Elías Gutiérrez Manuel

El Colegio de la Frontera Sur, Av. Centenario km 5.5, Chetumal 77014, Quintana Roo,

México. E-mail: [email protected], [email protected] The phylum Rotifera comprises of about 2000 described species worldwide. In general, this group group has some serious taxonomic problems, which are the result of various reasons; one of them is that rotifers exhibit high intraspecific morphological variation. This paper reports the first barcode analysis of a large number of monogonont rotifer species from Mexico. All specimens analyzed were based on field-collections from different waterbodies. We standardized the protocol to extract DNA and to amplify the gene cytochrome c oxidase 1 from a single specimen. Gene sequences were obtained from 461 specimens corresponding to 133 species. The average genetic divergence between conspecific individuals was 0.7%, while the genetic divergence between congenerics was 20%. Our data reveal possible cryptic speciation in Lecane bulla, L. cornuta, L. curvicornis, L. hastata, L. luna, L. lunaris, Brachionus calyciflorus, B. quadridentatus f. brevispinus, B. quadridentatus f. cluniorbicularis, Keratella cochlearis, K. tropica, Platyias quadricornis, Mytilina ventralis var. macracantha, Ascomorpha ovalis and Testudinella patina. The results indicate that the barcodes can be an important tool for taxonomic studies in rotifers. However, it is necessary to use samples from different geographic areas in order to have a more complete picture of genetic differentiation in these organisms. Keywords: rotifers, barcodes, Mexico, cryptic species, taxonomy.


18

Water dynamics and species richness of rotifers (Monogononta) in trout raceways in Xico, Veracruz

Garza-Mouriño Gabriela, Flores López Tello Josué, Contreras Tapia Rubén Alonso, Benítez Díaz-Mirón Marcela Ivonne, Vázquez Romero

María del Carmen, Zamora García Margarita and Castellanos-Páez María Elena

Calzada del Hueso 1100, Colonia Villa Quietud, Delegación Coyoacán, C.P. 04960, D.F. México, Tel. 5483-7000 Ext. 7181. [email protected]

We conducted a small study to determine the diversity of rotifers and the variability of the physicochemical parameters: temperature, pH and oxygen, in the raceways of rainbow trout (Oncorhynchus mykiss). The data were obtained from synoptic sampling of 96 hrs. The parameters were evaluated every hour to represent the hydrodynamics of the raceways; 54 isolines maps were generated showing the flows and the influence of the water input. The temperature ranged from 16° to 27°C with an average of 22.3° ± 2.5°C, while the pH ranged from 6.78 to 7.9 with an average of 7.35 ± 0.14. The oxygen showed values ranging from 5.52 mg·L-1 to 13.99 mg·L-1. We determined the flow and the water residence time in the raceways. Finally, we found a total of 10 taxa belonging to the genera Anuraeopsis, Brachionus, Epiphanes, Euchlanis, Lepadella and Lecane. Keywords: Rotifers, Oncorhynchus mykiss, raceways, Mexico, hydrodynamics.


19

Phytoplankton composition, diversity and relation with water trophic condition of Valle de Bravo reservoir, Mexico

Gaytán-Herrera Martha Leticia, Martínez-Almeida Víctor M. and Ramírez-García Pedro

Research and Postgraduate Division (UIICSE-CyMA Project), Universidad

Nacional Autónoma de Mexico/FES-Iztacala, Avenida de los Barrios No. 1, 54090 Tlalnepantla, Estado de Mexico, Mexico. [email protected] or

[email protected] Species composition and diversity are important criteria for evaluating the suitability of water for multiple purposes. We assessed the temporal and spatial variation of phytoplankton composition, abundance, species richness and evenness at five stations to predict the state of Valle de Bravo, the principal drinking water reservoir in central Mexico. Monthly surface water samples were analyzed for physico-chemical parameters and phytoplankton during February to November 2010. A total of 120 taxa were recorded: 22 Bacillariophyta, 51 Chlorophyta, 6 Chrysophyta, 5 Cryptophyta, 19 Cyanobacteria, 8 Dinophyta and 9 Euglenophyta. More taxa (74) were recorded between March and May. The mean phytoplankton abundance was characterized by two pulses: April-May ( 320 x 103 cel ml-1) and August ( 338 x 103 cel ml-1). Lowest and highest values of Shannon-Wiener diversity (0.50 and 1.45) and Pielou’s evenness indices (0.16 and 0.40) were reached before mixing (November) and after mixing (February), respectively. Comparison with collections made a decade ago (2000) indicated that Cyanobacteria remain the most abundant group but the dominant taxa are not the same. At present, Pseudanabaena mucicola and Microcystis wesenbergii prevailed (90-150 x 103 cel ml-1) in contrast with M. botrys and M. flos-aquae ( 205 x 103 cel ml-1) during earlier studies. The presence of certain cyanobacteria such as Cylindrospermopsis raciborskii, Dolichospermum (Anabaena) planctonicum, Limnothrix redekei, Lyngbya birgei, Microcystis aeruginosa, Planktothrix agardhii, Snowella septentrionalis and Woronichinia naegeliana are considered to be indicators of eutrophication and need special attention for their potential toxicity.


20

Optimal foraging by planktivorous fish at patchy distribution of Daphnia prey: a global-warming perspective

Gliwicz Z.M. and Maszczyk P.

Department of Hydrobiology, University of Warsaw, Poland, Banacha 2, 02-097

Warsaw, Poland, [email protected] Contrary to the common belief that aggregation is used as an antipredation defense in zooplankton, the individual risk of a planktonic animal (such as Daphnia) was found to increase rather than decrease within such assemblies, confirming that planktivorous fish preferentially feed within patches of prey. This was revealed in mesocosm experiments, with three different Daphnia species and two common planktivorous fishes (roach and perch), conducted in a system of 8 interconnected 1 m3 tanks with patchy Daphnia distribution, where fish were allowed to feed at dusk and dawn. The overnight decline in Daphnia density was always most dramatic in the tank with the highest Daphnia abundance (by 70-90% compared to 20-40% at low abundance). This was the result of the rapid relocation of fish between the tanks: 50-90% of fish assembled in the tank with the highest Daphnia density and remained there until light conditions allowed them to feed. Daphnia adults with eggs in their brood cavities were depleted more rapidly than juveniles. This was most apparent in tanks with low Daphnia density, where the fish cruising speed was distinctly higher, hence the energy gain from small-bodied prey was likely insufficient to cover the cost of each post-capture burst of acceleration. These findings imply that a planktivorous fish may change its foraging strategy, from the typical low-speed harvesting of small but abundant prey to high-speed hunting for larger but more scarce ovigerous females, when a higher energy gain is required to pay the increased costs of post-capture accelerations. These costs, however, may be much smaller at higher temperatures due to the lower water viscosity. Thus, reduced water viscosity as a consequence of global warming may strengthen the impact of fish on zooplankton and so weaken grazing on phytoplankton, leading to persistent cyanobacterial blooms in tropical lakes.


21

Long term patterns in the chlorophyll a concentration and vertical distribution in a tropical, deep lake

González Contreras Circe Guadalupe1, Alcocer Javier2 and Oseguera Pérez Luis A.2

1Programa de Posgrado en Ciencias del Mar y Limnología, UNAM. A.P, 70-305.

Colonia Universidad Nacional Autónoma de México. 04510. Delegación Coyoacán. México, D.F. e-mail: [email protected]

2Facultad de Estudios Superiores Iztacala, UNAM. Proyecto de Investigación en Limnología Tropical. Av. de los Barrios No.1, Los Reyes Iztacala, Tlalnepantla, Estado

de México 54090 México. Monthly vertical profiles of chlorophyll a concentration (Chl-a), temperature and photosynthetic active radiation (PAR) were carried out along thirteen years (1998-2010) in order to identify the temporal (seasonal and inter-annual) variations in the phytoplankton chlorophyll a concentration in Alchichica, a deep (62 m) and tropical Mexican lake. Alchichica is a warm-monomictic lake, mixing takes place in the dry winter (January-March) and stratifies the rest of the year. The euphotic zone was shallower (18.10 2.40 m) during the mixing (turbid water phase) and increases down to (23.19 3.31 m) along the stratification (clear water phase). Higher and homogeneous Chl-a concentrations are found during the circulation period as a result of the diatom bloom. During the onset of the stratification a cyanobacteria bloom develops, which results in high Chl-a concentrations close to the surface. Along the well-established stratification, a deep chlorophyll maximum (DCM) is observed at the metalimnion. The described pattern repeats every year with slight differences. Keywords: chlorophyll a, DCM, Alchichica, warm-monomictic, Mexico.


22

Development of crustacean plankton in shallow, polyhumic reservoir in the first 20 years after impoundment (NE Poland)

Górniak A.S. and Karpowicz M.

University of Bia ystok, Institute of Biology, Department of Hydrobiology,Swierkowa st. 20B, 15-950 Bia ystok, Poland. e-mail: [email protected]

Multiannual changes of structure and biomass of crustacean zooplankton were studied in the shallow, lowland, polyhumic Siemianówka Dam Reservoir (SDR) on the upper Narew River in NE Poland, with peatland and forest domination in the catchment without any important anthropogenic sources of water pollution. SDR was created in 1991 with area 32 km2 and volume of 80 Mm3 is polymictic, artificial lake with a long time of water exchange (mean 3 months). High ammonium and SRP ions, aviability for phytoplankton, low water transparency and high DOC concentration resulted in water humoeutrophication caused an intensive summer Cyanobacteria development. In the SDR Cyprynidae were promoted in the nekton. Population of effective Daphnia filtrators decreased after the first 5-7 years of SDR existence when population of fish predators active took part in the “top down” regulation of ecosystem. In the next years Crustacean structure has changed into detritivore and bacteriovores species with small body size and low mean biomass values (<2 mg/L). Increasing algal biomass and high benthivores fish population in SDR had affected in dominations of Daphnidae-Bosminidae- Chydoridae zooplankton complex, with 31 species Crustacea and Copepoda - mainly nauplii forms. First Sididae species were observed in the reservoirs in 10 years after river damming. Observed seasonal changes of body size and proportion of Daphnia cucculata caused by an intensive fish pressure on zooplankton and summer Cyanobacteria development. Without decrease of fish population, the lower trophy of reservoir is an impossible task.


23

Long-term variability of zooplankton in a mesotrophic lake - 90 years of Wigry Lake study in the Northeastern Poland

Górniak A.S., Ejsmont-Karabin J. and Karpowicz M.

University of Bia ystok, Institute of Biology, Department of Hydrobiology, Swierkowa st. 20B, 15-950 Bia ystok, Poland. e-mail: [email protected].

Wigry Lake (WL) has one of the longest zooplankton data sets in Poland. First investigation by Lity ski were made in the 1920s, by A. Karabin in the years 1970-1990 and present investigations in the years 2007-2010. Study of pelagial Rotifera started in 1930s and then lasted from 1970 up to present. This situation allows long-term analysis of zooplankton variability during 90 years with respect to changes in well documented trophic status of the main basin of the lake. Postglacial, dimictic WL has an area of 21.2 km2 and max. depth 73 m. It consists of a few basins connected by straights which together with bays and islands create very diversified morphometry. Up to middle of 1960 WL remained mesotrophic, with meso-eutrophic northern part of the lake. Strong anthropogenic eutrophication of its waters was observed in the years 1970-2000, due to loading of non-treated and partly treated sewages from Suwa ki City and villages located in the lake catchment. From 1999 come back to earlier situation is noted as a result of an establishment of the Wigry National Park and thus a commencement of the intensive water management project. The abundance and structure of pelagic zooplankton of Wigry Lake little has changed in 90 years. In 2007-2009 there were noted 15 species of Cladocera, 4 species of Calanoida, 6 taxa of Cyclopidae and 26 species of Rotifera. Generally, although rotifer and crustacean communities indicate a lack of changes in trophic status of the lake, zooplankton structure is slightly different in different parts of the lake. The presence of two rare for Polish waters species of Calanoida: Eurytemora lacustris and Heterocope appendiculata, as well as rotifer Conochilus hippocrepis indicates that the lake still remains mesotrophic.


24

Planktonic stoichiometry needs more attention at the PEG workshops

Gulati Ramesh D.

Netherlands Institute of Ecology, Wageningen, the Netherlands A review of literature on plankton stoichiometry shows that the ratio of carbon to phosphorus (C : P) in seston is a major determinant of energy transfer in aquatic food webs. This elemental ratio may vary more than an order of magnitude owing to various extrinsic and intrinsic factors. The environmental factors that directly lead to an increase of the C: P ratio (= decrease in P content) in seston are light intensity and water temperature, in addition to the extent of P limiting growth conditions. It seems that marine and freshwater ecosystems differ in N and P concentrations, N:P stoichiometry, and the distribution of N and P within the dissolved, seston, and zooplankton pools. There is some strong and consistent evidence of inverse relationships between the Daphnia abundance and the seston C:P ratio from both lake and laboratory studies. Also, particularly notable is higher proportion of the P, and to some extent N, incorporated in the particulate fraction (seston + zooplankton) of freshwater lakes, compared with marine sites. It seems zooplankton is physiologically confronted with the distinct seasonal shifts in the quality of lake seston. Direct P limitation is a very important factor determining food quality for zooplankters, especially daphnids, which have relatively the highest P content among the crustacean zooplankton. Moreover, Daphnia spp. are homeostatic in that they tend to keep their body P more or less constant and thus their C:P ratios fluctuate in a relatively narrow range (~10%). To achieve this constancy of body P, the daphnids compensate lower P content of their ingested food by expending more C energy, probably through their metabolic excretion (DOC release) and respiration rates in order to a conserve body P when this element is limiting. There is evidence from literature that Daphnia is a good model organism because of the way it can deal with P limitation caused by food limitation, particularly because of inferior quality food. In Daphnia magna P content of the algae has been shown to strongly affect both the growth rate and the feeding activity. While the feeding activity increases with declining food quality (increase in C:P ratio of edible phytoplankton), the growth rates are found to be maximal at intermediate C:P levels of food. Thus, the direct P limitation is a very important factor determining food quality for zooplankters. The influence of the P content of the food on the feeding activity of Daphnia offers a mechanistic explanation for the observed homeostasis in daphnids. The growth rate hypothesis (GRH) proposes that variations in C: P and N: P ratios of the organism reflect the variation in P content associated


25

with altered allocation to the P-rich ribosomal RNA under different growth rates. In addition to poor quality (high C:P ratios) of phytoplankton food, biochemical limitations (omega-3 fatty acids) and an increased resistance to digestion because of an increase in cell wall thickness of algal particles can limit zooplankton dynamics. Seemingly, the overall impact of P via food intake seems to be generally larger than the effect of omega 3-FA. P limitation via food quality, i.e, increased relative abundance of cyanobacteria in the food under P- limiting food conditions is also common for daphnids in many eutrophic lakes. In such cases, the impact of food limitation on zooplankton may perhaps even exceed that of the fish predation, particularly in shallow eutrophic lakes dominated by cyanobacterial phytoplankton. Lastly, one can anticipate from the existing literature studies on modeling the effects of the climate change on lake ecosystems, that the expected rise of water temperature and carbon dioxide concentrations, during the ongoing climate change, can affect the planktonic stoichiometry as well as zooplankton growth rates. An example of the effect of such a climate warming in lakes and other freshwater bodies will primarily manifest itself through an earlier by a few weeks the onset of thermal stratification, leading to a faster development of edible phytoplankton. Such a shift in the timing of phytoplankton development is likely to cause a miss-match because zooplankton development rate is likely to lag much behind that of phytoplankton.


26

Zooplankton structure and its relationship with deep chlorophyll maximum in a sinkhole in Quintana Roo, Mexico

Gutiérrez-Aguirre M. A. and Cervantes-Martínez A.

Universidad de Quintana Roo, Unidad Académica Cozumel, Depto. Ciencias y Humanidades; Cozumel, Quintana Roo, 77600. [email protected]

Presence of zooplankters on different layers of the water column can affect the vertical concentration of chlorophyll, through the grazing or by the mineralization of fecal material on superficial or deeper layers of water column. In a year–round study, a deep chlorophyll maxima (DCM) was present during rainy and winter storm seasons at 5-6 m depth in a meso-eutrophic, dissolution system, called El Padre. When DCM was present, dominant meso-zooplankters were Keratella americana, Brachionus havanaensis, T. inversus and nauplii. They were more abundant at 0.5, 2.5 and 5 m, suggesting their grazing in the upper layers of the system as an important factor for persistence of the DCM that ranged from 1.5 to 3 mg/l of chlorophyll a concentration. Presence of DCM was independent of the mixing conditions of the system, and higher oxygen concentration was recorded on metalimnion during the stratification. Presence of the DCM could be related to the low grazing on meta and hypolimnion layers in the system.

Key words: DCM, distribution, ecology, vertical.


27

Planktonic rotifers in hypertrophic conditions: is the N: P relationship important?

Guzmán Olivia, Lugo Alfonso, Peralta Laura, Sánchez Ma. Del Rosario, Oliva Ma. Guadalupe, Morlán Josué and Verver y Vargas Jaqueline

Proyecto de Limnología Tropical, UIICSE, FES Iztacala, UNAM. Av. de los Barrios No. 1 Los Reyes Iztacala, Tlalnepantla, Estado de México. C.P. 54500

In hypertrophic waters, N and P concentrations are very high, but frequently the N: P relationship is unbalanced, affecting the composition and nutritious quality of phytoplankton. Rotifer growth can be affected by food quality and quantity. In hypertrophic conditions, low values of the N: P relationship are common. That´s the case of Lake Tezozomoc, a shallow urban lake filled with secondary treated sewage water where previous studies measured N: P ratio <5. We studied the effect of N: P balanced relationship and the nutrient dilution on planktonic rotifers in a shallow hypertrophic lake. Three experiments were conducted along 2008 year using plastic closed microcosms (10 l): one in the cold-dry season, other at the warm-dry season and the last in the warm-rainy season. Three different treatments were used: 1) balanced N: P (16:1) lake water; 2) diluted (75%) unbalanced lake water and 3) lake water as control. Two replicates of each treatment (three in the last experiment) were used. Temperature, D.O. pH, K25 and Total N, P, and chlorophyll a concentrations were measured. Phytoplankton and zooplankton (including rotifers) composition and fluctuation were also evaluated. Twelve rotifer species were identified, being Brachionus angularis, B. calyciflorus, B. caudatus, Polyarthra vulgaris, Trichocerca pusilla and Cephalodella catellina the most abundant. No statistical differences (one way ANOVA, P>0.05) were found between treatments for rotifers densities for each experiment, but differences were found between seasons (ANOVA P<0.05). Phytoplankton along dry season was dominated by Chlorophyta species and rotifers were very abundant (up to 27500 ind l-1). Along the rainy season Cyanobacteria (mainly Microcystis spp.) was the dominant group and rotifer densities were lower (15600 ind l-1). There were no effect of nutrients balance or decrease on rotifers, but natural phytoplankton variation during the year favored the dominance of different rotifer species.


28

Preliminary study of the food content in tropical tadpoles (Ollotisvalliceps) and their predator-prey relationship with zooplankton in

an aquatic system in Cozumel, Mexico

Jacobson Brianna, Cervantes Martinez Adrian and Gahona Fuller Michelle

Universidad de Quintana Roo, Campus Cozumel, Quintana Roo 77642. [email protected]

In tropical latitudes the information available on the stomach contents of tadpoles is scarce. In this study we have been investigating the stomach contents of tadpoles (Ollotis valliceps) that inhabit an artificial aquatic tropical system located at: N 20 29’ 18.3” and W 86° 56’ 22.8”. The sample collection was performed in the months of January to December 2011. To obtain information about the stomach contents of the tadpoles we dissected 15 to 20 individuals per month and recorded the stomach contents found in their intestines. Additionally we have also been studying the abundance and richness of rotifers to observe if there is a predator-prey relationship that exists between tadpoles and rotifers. We have registered 14 rotifer species (belonging to the genus Brachionus and Lecane, and the group Bdelloidea). So far in the stomach contents of the tadpoles we found that preferred prey was the bdelloid rotifers (53.8%). We also found various individuals belonging to the benthic and zooplankton groups: ostracods (9.9%), cladocerans (0.1%), copepods (0.1%), rotifer eggs (28.2%), cladoceran eggs (7.9%), and phytoplankton. This is the first attempt at recording the food preferences of tadpoles in a Mexican tropical aquatic system.


29

Impacts of environmental factors on the physiology of algae and cyanobacteria

Juneau Philippe

Department of Biological Sciences-TOXEN, Ecotoxicology of Aquatic Microorganisms Laboratory, Université du Québec à Montréal, Montréal, Qc, C.P. 8888, Succ. Centre-

Ville, H3C 3P8, Canada. Water quality of our lakes, rivers and estuaries has a direct impact on many social and economic activities, such as fishing, swimming and tourism, and on the health of animals and humans. Due to its basal position, phytoplankton plays an essential role in aquatic ecosystems and any phytoplankton physiological condition impairment or modification of the community will have major consequences on the entire aquatic food web. Physiological state and growth of phytoplankton can be affected by xenobiotics (such as metals and pesticides), by natural occurring environmental factors (such as light and temperature), and by metabolites produced by algae and cyanobacteria (such as cyanotoxins). Although the effect of environmental factors on phytoplankton growth was extensively studied at the ecological level, factors controlling phytoplankton population dynamics at the cellular level are not yet well understood. We are therefore studying, at the physiological and biochemical levels, the complex interaction among these various factors affecting phytoplankton, and therefore altering water quality. In this presentation I will focus on the effects of some environmental factors (temperature, metals and herbicides) on the physiology of different phytoplankton species. This work provides additional information on the role of different environmental factors in algal and cyanobacterial population dynamics.


30

Genotype-genotype dependent interactions between the cyanobacterium Microcystis and its grazer, the waterflea of the

genus Daphnia

Lemaire V.1, Brusciotti S.1, van Gremberghe I.2, Vyverman W.², Vanoverbeke J.1, De Meester L.1

1Department of Aquatic Ecology and Evolutionary Biology, K.U.Leuven, Ch. Deberiotstraat 32, 3000 Leuven, Belgium. [email protected]

2Laboratory of Protistology and Aquatic Ecology, Ghent University, Krijgslaan 281 – S8, 9000 Gent, Belgium

Microcystis are cyanobacteria inhabiting many of the freshwater systems we use for recreation, drinking water, or fisheries worldwide. Microcystis blooms have a pervasive impact on their abiotic (e.g. low light levels, hypoxia) and also impact their biotic environment by producing secondary metabolites (e.g. microcystin-LR, protease inhibitors), which can poison or kill organisms spanning the entire foodweb, including humans and livestock. Large-bodied Daphnia are capable of ingesting cyanobacteria, but can Daphnia control Microcystis blooms or, is it rather Microcystis that suppresses Daphnia? Recent studies report Daphnia physiologically acclimatizing and genetically adapting to cyanotoxins. We hypothesized that interactions between Daphnia and Microcystis are genotype-genotype specific, the outcome of the interaction depending on the genetic identity of both. To test this, we exposed two-day old juveniles of ten Daphnia clones for 48 hours to increasing concentrations of ten Microcystis strains (supplemented with Scenedesmus to 1mgC/l). We observed a significant Microcystis strain effect on Daphnia mortality. These differences could only partly be attributed to differences in microcystine-LR content between the strains. We also observed a significant effect of Daphnia genotype on mortality caused by Microcystis. Finally, we confirm our hypothesis: there are genotype-genotype dependent interactions between Microcystis and Daphnia, indicating that there is scope for local co-adaptation of Microcystis and Daphnia, suggestive of a geographic mosaic of co-evolution. Microcystis evolved a portfolio of anti-grazer defenses, and in response Daphnia acquired different resistance mechanisms to circumvent defenses of Microcystis strains. We conclude that locally adapted Daphnia may be able to control cyanobacteria and prevent blooms. Keywords: Daphnia, Microcystis, cyanobacteria toxins, eco-evolutionary dynamics, genotype x genotype interactions, geographic mosaic of coevolution, harmful algal blooms, top–down control.


31

Heterogeneity of plankton distribution in a deep sub-alpine lake during summer (Lake Iseo – I)

Leoni Barbara1, Huang Peisheng2, Garibaldi Letizia1, Marti Clelia Luisa2

and Imberger Jörg2

1Dipartimento di Scienze dell’Ambiente e del Territorio, Università degli Studi di Milano-Bicocca, Piazza della Scienza 1, 20126 Milano, Italy

2Centre for Water Research, University of Western Australia, Crawley, Western Australia, Australia

The importance of various hydrodynamic processes, including water column stratification, internal wave tilting, surface current transportation and river inflow intrusion, to the spatial distribution of phytoplankton and zooplankton were investigated with field data collected during the summer, July 2010, in a typical deep sub-alpine lake located in northern Italy (Lake Iseo). During study period the water column was thermally stratified while the wind-induced surface current advection was strong, as typical during the summer season, resulting in significant vertical heterogeneity but weak horizontal heterogeneity of plankton distribution.


32

Life cycle and ecological role of Durinskia baltica (Dinophyceae: Peridiniales) in urban lacustrine environments (Xochimilco,

Mexico City, Mexico)

Lira Hernández Beatriz I.1 and Tavera Sierra Rosaluz2

1Posgrado en Ciencias del Mar y Limnología, Facultad de Ciencias, UNAM, A.P. 70-747, CU Coyoacán, 04510, D.F. C.P. 04510

2Laboratorio de Algas Continentales. Ecología y Taxonomía, Facultad de Ciencias,

UNAM, A.P. 70-747, CU Coyoacán, 04510, D.F. C.P. 04510. Populations of Durinskia baltica collected in the lake Xochimilco, were studied during the period September to December 2010 and January to September 2011. Life cycle was described in situ about living and preserved specimens documenting each stage using light microscopy. Cell morphology was described in light and transmission microscopy (TEM) and morphology of theca was described in detail using scanning electron microscopy (SEM). We analyzed the morphological characters that this species shares with other of close genera as Peridinium, Glenodinium and Peridiniopsis, arguing that the study populations should be assigned to the species proposed as Durinskia baltica. An assessment of D. baltica density allowed to infer the effect on the composition of the phytoplankton community in a place where it forms blooms (Japan Channel) and three sites where it occurs not abundant (Tláhuac lagoon). A statistical analysis showed that environmental factors can directly influence the formation of blooms, also closely linked with time of massive germination of resistance cysts present in the sediment. The current description of the biology and ecology of this species in freshwater environments of Mexico is the first record because its presence had not previously been studied. Key words: dinoflagellates, freshwater, eutrophic, blooms, cysts.


33

The effect of a small-size omnivorous fish on the plankton assemblage in a shallow hypertrophic lake: a mesocosm study

Lugo Alfonso Vázquez, Sánchez María del Rosario, Oliva María

Guadalupe, Peralta Laura, Morlán Josué, López S. Gabriel, Hernández Rosa Angélica and Alvarado Francisco

Proyecto de Limnología Tropical, UIICSE, FES Iztacala, UNAM. Av. De los Barrios No. 1 Los Reyes Iztacala, Tlalnepantla, Estado de México. C.P. 54500

Small size omnivorous fishes are common in tropical shallow lakes, and they consume zooplankton, phytoplankton, benthic invertebrates and detritus, exerting an important effect on the planktonic food web. In this study we investigated the effect of a small size omnivorous fish (“guppy”, Poecilia reticulata) on the planktonic assemblage in a shallow hypertrophic urban lake (Lake Tezozomoc, Azcapotzalco, Mexico City). Six 80 l mesocosms were used: three with 10 adult guppies (5 males and 5 females) each, and three without fishes. Mesocosms were open at the bottom, in contact with the sediments. Five weekly samples were made between August-September 2010 (the warm-rainy season). Temperature, D.O. pH, K25 and Total N, P, and chlorophyll a concentrations were measured. Phytoplankton and zooplankton composition and fluctuation were also evaluated. No statistical differences (one way ANOVA, P>0.05) were found between treatments for all the measured variables. Temperature range was 18.6- 22.9 ºC, K25 810-967 μS cm-1, D.O. 2.8 -11.5 mg l-1and pH ranged 8.5-9.6. Total P was 1.4-3.1 mg l-1 and Total-N 3.1-10.4 mg l-1. Chlorophyll a ranged 10-135 μg l-1 Phytoplankton was dominated by Microcystis flosaquae, Cryptomonas ovata, Anabaena spiroides, Chlorogonium minimum, Kirchneriella lunaris and Micractinium pusillum but more than 40 species were present. Thrirteen rotifer species were identified, being Brachionus angularis, B. calyciflorus, B. caudatus, Polyarthra vulgaris and Trichocerca pusilla the most abundant. Moina micrura (Cladocera) and Acanthocyclops americanus-robustus-vernalis complex (Copepoda) were the only crustacean zooplankton species found. No direct effect of fishes on phytoplankton was observed but a significant negative correlation (r2 = -0.640 P<0.05) was established between copepods abundance (higher in fishless treatment) and rotifers. When fishes were present, they predate on copepods, and rotifers could reach higher densities. We conclude that P. reticulata is not the main factor affecting the structure of the planktonic assemblage in hypertrophic conditions.


34

Destiny of autotrophic picoplankton in warm-monomictic and meromictic lakes?

Macek Miroslav 1,2, Peštová Dana1,3, Šimek Karel2, Bautista–Reyes Fernando1, Hernández-Avilés Justo Salvador1, Sánchez-

Medina Ximena1, Nixdorf Brigitte4, Picazo Antonio4, Camacho Antonio4

1National Autonomous University of Mexico, FES Iztacala, Dept.Tropical Limnology, Av. de los Barrios 1, 54090 Tlalnepantla, Edo. México, Mexico

2BiologyCentre, CAS, Institute of Hydrobiology, eské Bud jovice, Czech Republic 3Masaryk University Brno, Czech Republic

4University of Valencia, Burjassot, Valencia, Spain 5Brandenburg Technical University, Cottbus, Germany

The control of autotrophic picoplankton (APP) development was analysed in a maar crater athalassohaline warm-monomictic lake Alchichica, Alc (Puebla/Veracruz; Mexico), and compared with another one La Preciosa, LPr (Puebla, Mexico) and two meromictic lakes Waldsee, WS (Lausitia, Germany) and Laguna de la Cruz, LC (Cuenca, Spain). Numbers and biomass of APP were evaluated via autofluorescence and using the Image analysis. DAPI staining and fluorescently labelled bacteria technique were employed to count ciliates, heterotrophic (HNF) and mixotrophic flagellates, and to estimate their feeding rates. APP showed specific growth rate of maximum 10% per day that coincided with the maximum possible elimination by ciliates. During the early stratification period in Alc (APP 2×106cells ml-1), flagellates were the key factor in the elimination of APP, being mostly controlled by metazooplankton. The ciliates’ APP elimination rate depended strongly on D.O. and light, being maximum around the oxycline, coinciding with 0.1% - 1% of photosynthetic active radiation, PAR. APP persisted for prolonged periods in suboxic layers. Despite of differences in lakes’ limnology (alkaline, deep and warm-monomictic lakes Alc, LPr vs. karstic- LC and iron-meromictic WS), the anoxic boundary showed very similar pattern: APP-ingesting and mixotrophic ciliates were concentrated there, eukaryotic-symbionts possessing ciliates (e.g., Coleps sp. and Pelagothrix sp.) in an upper layer but APP feeding, possible mixotrophs (Alc, WS - Euplotes sp. and Alc, LPr, LC - Spirostomum teres) preferred a layer below. APP heterotrophic feeders (Alc, LPr - Cyclidium sp., LC - Ctedoctema sp.) migrated through the boundary but true anaerobic ciliates (Caenomorpha sp., odontostomatids) did not ingest APP. Generally, only a part of APP production could be incorporated into the plankton via the microbial loop. Combined use of sequestered APP-photosynthesis and digestion by ciliates in the anaerobic conditions with an optimum light (PAR below 0.2%) is hypothesized.


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Ecology of shallow reservoirs: strong effect of a dry-stand on subsequent cyanobacteria blooms and water clarity

MekonenTeferi1,2, De Bie T.1, Declerck S.A.J.8, Snoeks J.1, Abraha Gebrekidan3,4, Tsehaye Asmelash5, Tadesse Dejenie2, Bauer H.6, Deckers

J.S.7 and De Meester L.1

1Laboratory of Aquatic Ecology and Evolutionary Biology, Katholieke Universiteit Leuven, Belgium. [email protected]

2Department of Biology, Mekelle University, Mekelle, Ethiopia 3Department of Chemical Engineering, Laboratory of Applied Physical Chemistry and

Environmental Technology, Katholieke Universiteit Leuven, Belgium 4Department of Chemistry, Mekelle University, Mekelle, Ethiopia

5Department of Microbiology, Mekelle University, Mekelle, Ethiopia 6MU-IUC, VLIR Coordinator, Mekelle, Ethiopia

7Division Forest, Nature and Landscape, Katholieke Universiteit Leuven, Geo-instituut, Leuven, Belgium

8Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen,The Netherlands

To alleviate water shortage in the northern part of Ethiopia, many small reservoirs have been constructed which are rain fed. Many of these small, shallow reservoirs are characterized by severe water quality deterioration, with high turbidity and excessive algal blooms. A recent survey study involving 32 reservoirs revealed that most of the reservoirs are characterized by dominance of the small riverine fish Garra, while results of an enclosure experiment provided indications for an association between the presence of fish and the occurrence of toxic cyanobacteria blooms (Microcystis). In the present study, we took advantage of a natural whole-lake manipulation experiment caused by an exceptionally dry year. The extended drought period resulted in a significant part of the reservoirs to dry up completely in April-June 2009. This resulted in a fish kill, and we capitalized on this opportunity to test the effect of such a dry period and the associated fish kill on reservoir ecology. We studied 13 reservoirs, seven of which dried up in April- June and refilled again in July 2009, while six reservoirs did not dry up. We sampled all reservoirs in September 2009 and characterized their ecology in terms of physical and chemical characteristics as well as biota. In September 2010, we repeated the sampling, using three categories: six reservoirs did not dry up in 2009 nor in 2010, four dried up both in 2009 and 2010, and three dried up in 2009 but not in 2010. We compared ecological characteristics of reservoirs that did and did not dry up in the different years. In addition, we also analyzed data on these 13 reservoirs that were taken during a large survey in September 2004, to assess to what degree the liability to dry up of reservoirs impacts its general ecology (none of the study reservoirs dried up during the dry period of 2004). Our


36

results show a strong difference in the ecology of reservoirs that dried up in the dry season prior to the sampling campaign. Reservoirs that refilled after a dry-stand were characterized by a clearly lower fish biomass (several reservoirs remained fishless for several months, others got recolonized but at low densities), lower phytoplankton and cyanobacteria (Microcystis) biomass, higher water transparency, higher percentage macrophyte cover and lower nutrient concentrations (TP, TN). Drying of the reservoirs has a clear cut and strong effect on water quality in the reservoirs. Differences in fish biomass and transparency were also significant in 2004, during a year were none of the studied reservoirs dried up. This suggests that regular drying of the reservoirs strongly impacts reservoir ecology quite profoundly. Keywords: reservoir, Garra, Microcystis, cyanobactria, fish biomass, dry-stand, water clarity, transparency, phytoplankton biomass, macrophyte cover


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Trophic relationships between plankton and chironomids in the canals of Xochimilco, Mexico

Merló Galiazzi Angel and Zambrano Luis

Laboratorio de Restauración Ecológica, Instituto de Biología, UNAM, C.U., Mexico City, Mexico. Twt@ZambranoAxolote

Chironomids combine elements of detritus and plankton (mainly phytoplankton) into their diet, thus link planktonic-benthic patterns of the ecosystems. However, these feeding habits may vary depending on factors such as eutrophication and changes in the land use. In addition, the feeding habits of chironomids are considered as indicators of ecosystem health. The aim of this study was to determine whether the eutrophication of Xochimilco has led to a change in the feeding patterns of chironomids. For this, samples of sediment, pelagic material and chironomids were collected from 64 sites in the canals of Xochimilco. The samples were processed using the standard protocol for stable isotope analysis of carbon and nitrogen. Linear regressions suggest that chironomids showed a change in their feeding pattern from benthic to pelagic material. In addition, relationship with the particulate organic matter (POM) was contrary to the expected outcome, indicating that other items are being incorporated into their diet. Products of bacterial activity could be the main factor in this change. This change in the feeding patterns of chironomids suggests a change in the lake ecosystem.


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Climate change and cyanobacterial nuisance

Lürling Miquel1,2

1Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA, Wageningen, The

Netherlands 2Department of Aquatic Ecology, Netherlands Institute of Ecology, Droevendaalsesteeg 10, 6708 PB, Wageningen, The Netherlands

There is great consensus that global warming will cause more frequent, longer lasting and more intense cyanobacterial blooms. One of the underlying assumptions is that cyanobacteria have higher growth rates at high temperatures than their eukaryote competitors. This hypothesis was tested experimentally by running a controlled experiment with eight cyanobacteria and eight chlorophytes at six temperatures in the range from 20 to 35°C. Based on the experiment and a literature survey the hypothesis could be refuted. However, short term competition experiments showed that Microcystis could outcompete potent chlorophyte competitors at high, but not at low temperature. Moreover, cyanotoxin concentrations were much lower at high temperature than at low temperature, and significantly influenced by the presence of a competitor. Subsequently, bioassays were conducted with natural seston from different water bodies covering a broad range from oligotrophic to hypertrophic conditions and subjected to temperature and nutrient manipulations. The results show that when competitors and grazers are present, the response of cyanobacteria to warming is stronger than the response of eukaryote algae. The effect of nutrients overrules this temperature effect with enhanced nutrient loadings favouring cyanobacteria. Cyanobacteria blooms might be aggravated in our changing world, especially through increased nutrient availability, however, elevated temperature might decelerate a concomitant increase in cyanotoxin concentrations.


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Introduction to the Symposium of the SIL Working Group on Plankton Ecology: The importance of Plankton Ecology, now and

in the future

Lürling Miquel1,2



Plankton ecology is a core discipline of limnology and marine biology as plankton plays a central role in the functioning of open-water systems. Plankton ecology contributes significantly to ecological theory building, because plankton communities are relatively easy to manipulate, have short generation time and a relatively small set of traits making them an ideal experimental model system for addressing both general ecological questions as well more system-specific questions. Our environment is changing at an unprecedented rate, demanding even more predictions from plankton ecology on the consequences of global change. I will give a short overview of the PEG and illustrate the broad area plankton ecology can contribute.


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Is the water hyacinth an efficient refuge for zooplankton against visual predation?

Montiel-Martínez Aideé1 and Ciros-Pérez Jorge2

1Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México. 2Proyecto de Investigación en Limnología Tropical, FES Iztacala, Universidad

Nacional Autónoma de México, A. P. 314, 54090 Tlalnepantla, Edo. Méx., México. Water hyacinth is the most problematic water weed of the world. Even though it is known that water hyacinth alters the dynamics in aquatic ecosystems (affecting biodiversity and food web), studies on its ecological interactions are still scarce. Macrophytes are not important for zooplankton as food resources, but they seem to be necessary for its survivorship in the presence of visual predators (e.g., planktivorous fishes). The role of aquatic plants as refuge against predators in temperate shallow lakes has been showed in several studies. In contrast, there are some zooplankters (e.g., Daphnia obtusa) that avoid plants even when kairomones are present. Macrophyte-fish-zooplankton interactions may be more complex in tropical and subtropical water bodies where information is even scarcer. Thus, the aim of this research is to elucidate whether tropical cladocerans avoid or use water hyacinth as refuge against vertebrate predation in the channels of lake Xochimilco, Mexico. Field zooplankton samples were monthly collected during a year in 6 channels: three wide (5-10 m) and three narrow (1-3 m), all of them sampled in two contrasting habitats, with and without Eichhornia crassipes. Additionally, in order to identify the role of E. crassipes in zooplankton behavior under predation risk, we conducted habitat choice experiments in laboratory conditions. Preliminary results show low densities and biodiversity of cladocerans (8 species) in the wild. Higher densities of cladocerans (at least twice times higher) were founded under water hyacinth mats in the two types of channels (wide and narrow channels). Moreover, habitat choice experiments suggest that Simocephalus vetulus neither avoided nor preferred water hyacinth when kairomones were absent. Contrarily, when kairomones were added a major proportion of organisms moved to E. crassipes. Hence, our preliminary results show that water hyacinth is not avoided by cladocerans in Xochimilco and suggest that it is efficiently used as refuge.


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Climate change, plankton and freshwaters: about what should we be worried?

Moss Brian

School of Environmental Sciences, University of Liverpool, UK

Climate change has historically had significant effects in Mexico and Central America, with suggestions that the Mayan civilisation may have dwindled round 900 AD because of drought and crop failure, whilst water supplies, ably managed by the Aztecs, have since become threatened as Mexico City has burgeoned in a warming phase. Predictions are that Mexico will become somewhat warmer and much drier in the present century and water quality and quantity have become major issues for Mexico City. The lakes on which the city was founded have mostly been drained and the remains of Lake Xochimilco are heavily eutrophicated. Lakes everywhere are showing signs of effects of human activities, but the local situation epitomises a more general problem of what the key problems really are. There is no shortage of evidence that lakes are warming, that the period of ice cover, (where ice forms), is diminishing, that stratification periods are lengthening and strengthening, and that nutrient loads in many areas are increasing with increased winter rainfall. In turn, events in lakes, like the spring diatom peak, and the peak spring populations of zooplankters, are occurring earlier and there are community and abundance changes among phytoplankters and zooplankters. Space for time studies suggest that cyanobacteria will become more abundant with warming and that fish communities will change more towards small omnivorous fish with a decline in piscivores, an increase in zooplanktivory, and a consequent decline in grazing on algae. A general scheme can be created that accounts for all of these phenomena, but its main features have been known for some time and there appears to be little predictability about the details of how particular species will behave. The situation is made even more unpredictable by evolutionary responses of microorganisms, zooplankters and even fish that may buffer induced effects, and by the uncertainties of how warming will progress. We can interpret in hindsight but we cannot predict beyond generalities. All of the expected changes represent the sort of weather driven fluctuations experienced in lakes between years and in reality pose little additional threat either to lake functioning or human dependencies. Other threats such as eutrophication are likely to remain much more important than climate change and although climate change reinforces the symptoms of eutrophication, it is unlikely to worsen the situation a great deal. Need we thus not worry about the effects of climate change and should we not concentrate on other aspects of lake degradation? In terms of the plankton system, the answer is likely to be


42

yes, but in terms of the whole lake system, there are grounds for much deeper concerns. The recent development of ideas concerning processing of organic matter in freshwaters is highly relevant. Much of the net production in mature terrestrial and swamp systems is either stored in lake sediments, or respired in lake communities. Experimental studies are showing a marked increase in this respiration, with consequences for carbon emissions to the atmosphere and potential positive feedback effects on warming mechanisms. It is perhaps in the gross features of ecosystem metabolism rather than in the minutiae of planktonic community changes that we should have most concern.


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Particulate carbon and chlorophyll-a fluxes in a tropical, oligotrophic Lake

Pascoe Tania1, Alcocer Javier2 and Oseguera Luis A.2

1Programa de Posgrado en Ciencias del Mar y Limnología, UNAM,.A.P, 70-305. Colonia Universidad Nacional Autónoma de México. 04510. Delegación Coyoacán.

México, D.F. e-mail: [email protected] 2Facultad de Estudios Superiores Iztacala, UNAM. Proyecto de Investigación en

Limnología Tropical. Av. de los Barrios No.1, Los Reyes Iztacala, Tlalnepantla, Estado de México 54090 México.

Until recently, the role of inland waters in the regional and global carbon balance had been considered unimportant. Particularly, there are few studies carried out in tropical lakes. Four sediment trap stations were located in a longitudinal transect (center to shoreline) in tropical and oligotrophic Lake Alchichica to evaluate the particulate organic carbon (POC), total particulate matter (TPM) and chlorophyll-a (Chl-a) fluxes. COP fluxes varied between 181 and 772 mg m-2 d-1, TPM 609 to 4460 mg m-2 d-1 and Chl-a fluxes between 0.9 and 8.8 mg m-2 d-1. The highest fluxes were found during the onset of the stratification (April-June) mostly related to the winter diatom bloom. The large and heavy diatoms are easily exported to the bottom. During the onset of the stratification a cyanobacterial Nodularia spumigena bloom takes place. These cyanobacteria have efficient floatation mechanisms that impede their exportation to the bottom but rather their transport close to the shore where they are further deposited. The fluxes close to the shoreline resulted higher (around twice) than those at the center of the lake. COP, TPM and Chl-a fluxes in Lake Alchichica are higher than those found in other oligo, meso and even eutrophic temperate and tropical lakes. Keywords: POC, Carbon sink, Chlorophyll a flux, Tropical lake, Oligotrophic lake, Mexico


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Chlorophytes like indicators of functional diversity in Xochimilco lacustrine area

Ponce-Mendoza A.1, Figueroa G.1, Ramos M.G.2 and Ferrara M.J.1

1Departamento El Hombre y su Ambiente and 2Departamento de Producción Agrícola

y Animal, Universidad Autónoma Metropolitana, Unidad Xochimilco. Calzada del Hueso 1100, Col. Villa Quietud. C.P. 14640.

Xochimilco lacustrine area (XOCH), in Mexico City, is a small heterogeneous freshwater system that has been transformed into a network of canals, small lakes, and wetlands. XOCH has been intensively managed. This system receives urban and agricultural waste, with resulting impacts on water quality. Pollution, quantity of water, loss of endemic species and the introduction of exotic species -like perch and tilapia- are some of the problems in the XOCH. Few works has been developed in the measure of Functional diversity (FD). FD has the largest impact in the productivity and ecosystem process. As chlorophytes are an important element in the physical-chemical cycles, we measure the three independents components of FD: richness, evenness and divergence, in chlorophytes species in 12 different sample sites in the XOCH. FD was measured with six different taxonomic and morphologic traits. In XOCH was found 42 species, mainly from the family: Scenedesmaceae (40%), Hydrodictyaceae (14%), Oocystaceae (19%). Functional evenness and richness were similar in XOCH with low values (p < 0.05). Tlicuili, Texhuilo y Apatlaco sample sites showed higher functional divergence than the other sample sites (p < 0.05). Urban lakes and rivers had many influence with dramatics changes. Low values in Functional richness and evenness means that some resources are unused and the niche space are under-utilized. Tlicuili, Texhuilo y Apatlaco, had higher values of functional divergence; three species were characteristics of those stations: Scenedesmus bicauda, Oocystis parva and Pediastrum duplex. Therefore, these species can be used as indicators of high values of divergence.


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Relationship between positive associations in freshwater bryozoan and zooplankton

Reyes-Flores Montserrat Delfina, Silva-Briano Marcelo and Adabache-Ortiz Araceli

Universidad Autónoma de Aguascalientes. Centro de Ciencias Básicas. Edificio No. 202. Departamento de Biología. Laboratorio No. 1, de Ecología. Av. Universidad No.

940. Ciudad Universitaria. C. P. 20131. Aguascalientes, MÉXICO. Tel: 52 (449) 9107400, ext. 347; Fax: 52 (449) 9108401. E-mail: [email protected]

The interactions between organisms in confined spaces favor different associations which are disadvantages to some species indirectly; the objective of this study is to provide photographic evidence of these associations in freshwater Bryozoans species (benthic invertebrates) and the possible impact on the zooplankton. Direct samplings were conducted in 8 different dams in the state of Aguascalientes. To Lophopodella carteri and Fredericella browni no associations were found while Plumatella repens and P. casmiana associations are commensal (tanatocresis) with ciliate Paramecium sp and epibiosis with Vorticella sp., Stentor sp. and rotifers of the Class Bdelloidea. These relationships provide strategies to increase the survival of these organisms and zooplankton provide disadvantages as an important source of food as the alga Chlorella sp. suspension remains difficult to catch because of the symbiotic relationships with Paramecium sp., and Stentor sp. The study of the relationship between positive associations and negative effects on other species that are part of food chains is an important area of expertise to understand the functioning of aquatic ecosystems. Keywords: Zooplankton, freshwater Bryozoans.


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Zooplankton richness and diversity in the reservoir Valerio Trujano, Tepecoacuilco, Guerrero, Mexico

Reyes Vanegas Gladis, Vázquez Sánchez Aurora, Nandini S. and Sarma

S.S.S.

Laboratory of Aquatic Zoology, Division of Research and Post-graduate Studies, National Autonomous University of Mexico Campus-Iztacala, Av. de Los Barrios # 1,

Los Reyes, Iztacala, Tlalnepantla, State of Mexico, Mexico. Information on the richness and diversity of zooplankton, particularly rotifers, cladocerans and copepods is meager for the large majority of states in Mexico including Guerrero. In this study we analysed the diversity of these three major zooplankton groups in the Valerio Trujano reservoir over a period of one year. Zooplankton was collected at five sites in the littoral and five in the center of the reservoir from March 2010 to February 2011. We collected samples once a month and analyzed various physiochemical parameters (temperature, pH, dissolved oxygen, nitrates and phosphates). Eighty litres of lake water was filtered from each of the sites using a 50 μm plankton net. Here we present data on the richness of rotifers, cladocerans and copepods from selected sites and during the warm (March and April; mean temperature 28°C) and cold (November and December; mean temperature 22°C) months of the year. We recorded more than fifty species of rotifers, six species of cladocerans, three cyclopoids copepod species and one calanoid copepod. The dominant taxa included Mastigodiaptomus montezumae, Thermocyclops inversus, Ceriodaphnia lacustris, Moina micrura, Diaphanosoma c.f. fluviatile, Wolga spinifera, Brachionus falcatus and Horaëlla thomassoni. The data have been analyzed with emphasis on the species richness and the male:female ratio of copepods in this tropical reservoir.


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The response of zooplankton community composition, productivity and phytoplankton-zooplankton transfer efficiency to

an experimentally deepened thermocline

Sastri A.R., Juneau P. and Beisner B.E.

Department of Biological Sciences, University of Quebec at Montreal, C.P. 8888, Succ. Centre Ville, Montreal, QC, H3C 3P8, Canada. [email protected]

Patterns of thermal stratification in North Temperate lakes are predicted to change in response to climate change induced variation in wind stress, precipitation, water clarity and temperature. Long-term observations and experimental manipulations note the dominance of smaller-bodied zooplankton groups in more heavily mixed systems. However, it is not clear how these compositional responses will be reflected in zooplankton community productivity and phytoplankton to zooplankton transfer efficiency. In this whole-lake study, we focused on the response of the crustacean zooplankton community to an experimentally lowered thermocline. Rates of crustacean zooplankton biomass production and phytoplankton production were monitored weekly in a lake in which the thermocline was experimentally lowered in one of three basins by mixing throughout the summer; a second basin also experienced a lowered thermocline without mixing while a third acted as a control. Crustacean zooplankton community productivity was estimated as the rate of chitobiase (crustacean moulting enzyme) production. Primary production rates were measured using PAM fluorometry. Comparisons of the mean of the date-specific differences between basins and experimental versus control years yielded significantly enhanced rates of secondary production that may be ascribed to the combined effects of mixing and thermocline deepening. The effect of the measured crustacean zooplankton community response on the plankton food-web will be discussed in the context of differences in zooplankton composition and phytoplankton to zooplankton transfer efficiency.


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Geographical distribution study of the Family Lecanidae (Rotifera: Monogononta) in Mexico

Serranía-Soto C. R.1 and Sarma S.S.S.2

1Posgrado en Ciencias Biológicas Universidad Nacional Autónoma de México.

e-mail: [email protected] 2Laboratorio de Zoología Acuática, FES Iztacala, UNAM, Av. de los Barrios No 1.,

Tlalnepantla de Baz, Estado de México, CP54090, Mexico. One of the most diverse genera of rotifers in the tropics is the genus Lecane of the Family Lecanidae. The Lecane has three subgenera: Lecane Nitzsch, 1827; Monostyla Ehrenberg, 1830 and Hemimonostyla Bartos, 1959. Three subgenera in all have about 163 valid species. Lecane species live in littoral habitats; many of them are cosmopolitan, but a few of them are restricted to certain habitats. The wide range of distribution of many species of Lecane can be explained by the following reasons: 1) passive dispersal, 2) short life cycles and 3) high fecundity. The aim of this study was to determine the diversity and distribution of the Lecanidae in Mexico. Samples were collected from different waterbodies (ponds, rivers, lakes and reservoirs) located in the State of Mexico, Veracruz, Tabasco and Chiapas. Some of the aquatic ecosystems from these states belong to the Lerma Santiagio, Grijalva-Usumacinta or Papaloapan hydrological regions. So far, 32 species of Lecane have been recorded. In the Rio Blanco 21 species were found. In Chimaliapan 15 species and in a highway pond from Veracruz to Alvarado 12 species were observed. Other waterbodies have fewer than 10 lecanid rotifers. L. bulla, L. closterocerca, L. hamata and L. pyriformis are considered the most common being present in 50% or more of the aquatic systems studied.


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Summary of species new to science that have been found in the State of Aguascalientes, Mexico

Silva Briano Marcelo and Adabache Ortiz Araceli Universidad Autónoma de Aguascalientes. Centro de Ciencias Básicas. Edificio 202. Laboratorio No. 1, de Ecología. Departamento de Biología. Av. Universidad No. 940. Ciudad Universitaria. C. P. 20131. Aguascalientes, Ags. Tel: 52(449) 9107400, ext.

347. Fax: 52(449) 9108401. E-mail: [email protected] In the state of Aguascalientes, Mexico, we have found several species new to science, which belong to the three groups of zooplankton: Rotifera (Brachionus josefinae Silva-Briano & Segers, 1992; Keratella mexicana Kutikova & Silva-Briano, 1995; Brachionus araceliae Silva-Briano Galvan-De la Rosa, Perez-Legaspi & Rico-Martinez, 2007), Cladocera (Macrothrix mexicanus Ciros-Perez, Silva-Briano & Elías-Gutiérrez, 1996; Macrothrix smirnovi Ciros-Pérez & Elías-Gutiérrez, 1997; Macrothrix sierrafriatensis Silva-Briano Quang Dieu, Dumont, 1999; Karualona penuelasi Dumont & Silva-Briano, 2000). Copepoda (Acanthocyclops dodsoni Mercado-Salas & Suárez-Morales, 2006; Acanthocyclops marceloi Mercado-Salas and Suárez-Morales, 2009; Acanthocyclops caesariatus Mercado-Salas and Suárez-Morales, 2009). These three groups have been found in the State of Agauscalientes and have provided several endemic species new to science and so in future collections, there exists the probability of finding new species. Keywords: Zooplankton, Rotifera, Cladocera, Copepoda, endemic species.


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How water-level fluctuations affect phytoplankton assemblages in a high altitude, tropical reservoir, Valle de Bravo, Mexico

Valeriano Riveros María Elena1,2, Vilaclara Gloria2, Merino-Ibarra Martín3

and Castillo Fermín Sergio3

1Posgrado en Ciencias del Mar y Limnología, ICMyL , UNAM. Circuito Exterior S/N.

Ciudad Universitaria, México, D.F. 04510. 2FES-Iztacala, UNAM. Av. de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, Edo. de

México, C.P. 54090. 3Instituto de Ciencias del Mar y Limnología, UNAM. Circuito Exterior S/N. Ciudad

Universitaria, México, D.F. 04510.

Valle de Bravo reservoir, an important component of the Cutzamala system which provides drinking water to the most populated area in Mexico, has been affected by strong water-level fluctuations due to water scarcity in the region during 2008-2009. To understand the responses of phytoplankton to water-level decreases, limnological monitoring was performed monthly for two years. The reservoir maintained its warm monomixis behavior (mixing from November to February) even when the water had fallen by 12 m below capacity. However, we did find indirect evidence (a progressive increase of the hypolimnetic temperature) of enhanced boundary mixing events, which are attributed to internal waves produced in VB by strong diurnal winds. The resulting nutrient inputs to the epilimnion, together with high (>20°C) temperatures, could explain the enhanced phytoplankton biomasses found during stratification. In contrast, we observed unusually low biomass during the circulation, probably due to low light availability (Zeu/Zmix<1), grazing and lower temperatures (from 17 to 20°C), which do not favor the diatoms and cyanoprocariota that bloom during stratification. Dominant species in the reservoir were Cyclotella ocellata, Fragilaria crotonensis, Woronichinia naegeliana, Microcystis wesenbergii, Mougeotia sp., and Closterium spp. Nitrogen-fixing cyanoprokariota (Nostocales), a recurrent problem in the reservoir, decreased markedly when compared to high water-level periods (i.e., 2001-2005), probably owing to the nutrient inputs, especially of nitrogen, from the hypolimnion. Nevertheless, evidence of N limitation was found at the same times that heterocyte formation was observed. We propose that this trait might be a better proxy for limitation than N concentration and N:P relationships alone. We conclude that a marked water-level decrease in Valle de Bravo reservoir results in increasing biomasses of planktonic diatoms, and a significant decrease in obnoxious algae such as Nostocales, thus ameliorating the system. Keywords: Reservoir, water-level decrease, phytoplankton, enhanced diatom biomasses, stratification.


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On the sudden occurrence of Microcystis in Lake Rauwbraken (The Netherlands) after the novel ‘Flock & Lock’ lake restoration

technique: do we understand what’s going on?

van Oosterhout Frank1 and Lürling Miquel2



We combined a low dose flocculent (Polyaluminiumchloride) with a lanthanum enriched benthonite clay (Phoslock®) into a novel restoration technique ‘Flock & Lock’. This treatment was first applied in April 2008 to Lake Rauwbraken (The Netherlands), where it stripped all phosphorus (P) from the water column and strongly reduced P release from the sediment. The treatment had a strong positive effect on water quality, i.e. cyanobacteria were removed, chlorophyll-a concentration dropped to very low levels of 3 ( 5) μg l-1, while before the application long term annual average was 20 ( 36) μg l-1. Total phosphorus concentrations were high before the treatment (median 144 μg P l-1), but were reduced to 8 μg P l-1 in the three years after the Flock & Lock treatment. Despite this regime shift from a turbid to a clear water state, low amounts of cyanobacteria accumulated near the shores each summer/autumn. We tested the hypothesis that these cyanobacteria (predominantly Microcystis) could originate from the seed bank in the sediment. That the inoculation from the sediment did not give rise to the development of cyanobacteria blooms supports the effectiveness of the Flock & Lock treatment in mitigating cyanobacteria nuisance in Lake Rauwbraken.


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Role of zooplankton in the food web of oligotrophic cenotes

Zambrano Luis and Santos Patricia

Laboratorio de Restauración Ecológica, Instituto de Biología, UNAM C.U., Mexico City, Mexico. Twt@ZambranoAxolote

The importance of zooplankton in lakes is associated with their position in the trophic structure between phytoplankton and secondary consumers. However, in tropical oligotrophic lakes, this position may be occupied by benthic organisms. This is because phytoplankton production can be greatly reduced if fish stocks are not properly maintained. The cenotes (sinkholes) of the Ecological Reserve of Sian Ka'an are ideal to understand the importance of these routes since they are tropical oligotrophic systems. Samples of zooplankton, insects and fish were collected in 6 cenotes to analyze their relative abundance and the identification of groups and isotopic composition. The isotopic composition will help to define the trophic position of each of the groups collected. In all waterbodies, there was a great diversity of zooplankton and insects but the abundances were low. Fish were identified as the third trophic level while insects and zooplankton as prey. The trophic position of each group varied depending on the waterbody. In shallow sinkholes most important prey are insects, while in deep waterbodies it the zooplankton. Zooplankton in shallow sinkholes is a main food for fishes during the larval stages but later the predators opted for diets in the trophic level occupied by the insects.


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Author Index


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Abraha Gebrekidan 35-36 Adabache Ortiz Araceli 45,49 Aguilar-Acosta Claudia Romina 14 Alcántara-Rodríguez J.A. 9 Alcocer Javier 2, 21, 43 Alillo-Sánchez José Luis 1 Alvarado Francisco 33 Ardiles Vilma 2 Arroyo Castro Jovana 3 Barrera-Moreno O.A. 9 Bauer H. 35-36 Bautista–Reyes Fernando 34 Beisner B.E. 47 Benítez Díaz-Mirón Marcela Ivonne 4, 6,18 Brenda Karen González Pérez 8 Brusciotti S. 30 Calderón Eva 5 Camacho Antonio 34 Castellanos-Páez María Elena 4, 6,18 Castillo Fermín Sergio 50 Cervantes Martinez Adrian 3, 7, 27, 28 Chaparro-Herrera Diego de Jesus 8 Ciros-Pérez Jorge 9,40 Contreras Tapia Rubén Alonso 6,18 Córdova Tapia Fernando 10 De Bie T. 35-36 De Meester L. 30, 35-36 Deblois Charles P. 11 Deckers J.S. 35-36 Declerck S.A.J. 35-36 Dumont Henri J. 12 Ejsmont-Karabin J. 23 Elías Gutiérrez Manuel 17 Esmeralda Bravo-Hernández 8 Espinosa-Rodríguez Cristian Alberto 13 Fernandez Rocío 14 Ferrara M.J. 44 Figueroa G. 44 Figueroa-Sánchez Michael Anai 14 Flores López Tello Josué 18 Gahona Fuller Michelle 28


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Gama-Flores José Luis 15 García Morales Alma Estrella 17 García-García Gerardo 16 Garibaldi Letizia 31 Garza-Mouriño Gabriela 4,6,18 Gayosso-Morales Manuel Aaron 14 Gaytán-Herrera Martha Leticia 1,19 Gliwicz Z.M. 20 Gómez-Cabral Gisela Carmen 13 González Contreras Circe Guadalupe 21 Górniak A.S. 22,23 Gulati Ramesh D. 24-25 Gutiérrez-Aguirre M. A. 7,26 Guzmán Olivia 27 Han Bo-Ping 12 Hernández Rosa Angélica 33 Hernández-Avilés Justo Salvador 34 Huang Peisheng 31 Huidobro-Salas María Elena 15 Imberger Jörg 31 Jacobson Brianna 28 Jiménez-Contreras Jorge 16 Juneau P. 11,29,47 Karpowicz M. 22, 23 Lemaire V. 30 Leoni Barbara 31 Lira Hernández Beatriz I. 32 Lomelí-Ramírez, N.A. 9 López S. Gabriel 33 López-López, B. 9 Lugo Alfonso 27, 33 Lürling Miquel 38,39,51 Macek Miroslav 34 Marti Clelia Luisa 31 Martínez-Almeida Víctor M. 1, 19 Martínez-Téllez Aurora 13 Maszczyk P. 20 Medina Palomo Carolina 3 MekonenTeferi 35-36 Merino-Ibarra Martín 50 Merló Galiazzi Angel 37


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Montiel-Martínez Aideé 40 Moreno-Gutierrez Rosa Martha 16 Morlán Josué 27, 33 Moss Brian 41-42 Nandini S. 8, 13, 14,16, 46 Nixdorf Brigitte 34 Oliva Ma. Guadalupe 27, 33 Ortega-Mayagoitia, E. 9 Oseguera Luis A. 2, 21, 43 Pascoe Tania 43 Peralta Laura 27, 33 Peštová Dana 34 Picazo Antonio 34 Piedra-Ibarra E. 9 Ponce-Mendoza A. 44 Ramírez-García Pedro 1,19 Ramos M.G. 44 Reyes Vanegas Gladis 46 Reyes-Flores Montserrat Delfina 45 Rietzler Arnola C. 12 Rivera De la Parra Ligia 13 Sánchez Ma. Del Rosario 27, 33 Sánchez-Medina Ximena 34 Santos Patricia 52 Sarma S.S.S. 8,13, 14, 15, 16, 46, 48 Sastri A.R. 47 Serranía-Soto C. R. 9, 48 Silva Briano Marcelo 45, 49 Šimek Karel 34 Snoeks J. 35-36 Tadesse Dejenie 33 Tavera Rosaluz 5, 32 Tsehaye Asmelash 35-36 Valencia Vargas Meetztli Alejandra 8 Valeriano Riveros María Elena 50 van Gremberghe I. 30 van Oosterhout Frank 51 Vanoverbeke J. 30 Vázquez Romero María del Carmen 6,18 Vázquez Sánchez Aurora 46 Verver y Vargas Jaqueline 27


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Vilaclara Gloria 50 Vyverman W. 30 Xu Kui 11 Zambrano Luis 10, 37, 52 Zamora García Margarita 6,18 Zamora-Barrios Cesar Alejandro 14


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D I R E C T O R I O

RECTORÍA Dr. José Narro Robles

Rector Dr. Eduardo Bárzana García

Secretario General Lic. Enrique del Val Blanco

Secretario Administrativo Dr. Francisco José Trigo Tavera

Secretario de Desarrollo Institucional Mtro. Miguel Robles Bárcena

Secretario de Servicios a la Comunidad Lic. Luis Raúl González Pérez

Abogado General Enrique Balp Díaz

Director General de Comunicación Social F E S IZACALA Dr. Sergio Cházaro Olvera

Director Dr. Claudio Antonio Carpio Ramírez

Secretario General Académico M. en C. Ángel Morán Silva

Secretario de Desarrollo y Relaciones Institucionales Dra. Laura Evelia Torres Velázquez

Secretaria de Planeación y Cuerpos Colegiados Lic. Eliseo Venegas Alvarado

Secretario Administrativo Dra. Carmen Yolanda Guevara Benítez

Jefa de la División de Investigación y Posgrado

Abstracts of the SIL Plankton Ecology Group. Mexico City, Mexico,12-18 February, 2012

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Additional Abstracts


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Long term perspectives of zooplankton record: case study of the Lake Kinneret (Israel) copepod assemblages

Gophen Moshe

Migal-Galilee Technology center, POB 831 Kiryat Shmone Israel (11016) [email protected]

Long term (1969-1990) record of zooplankton biomass distribution in Lake Kinneret indicates an averaged composition of Cladocera-58%, Copepoda-35%, and Rotifera-7%. The age composition of the copepod assemblages represented a permanent mixed age structure, i.e. all stages were recorded in all months, all years, all sampling stations and depths. Mesocyclops ogunnus and Thermocyclops dybowskii are dominant species and Eucyclops serrulatus and Eudiaptomus drieschi were rarely recorded as well. The biology of M. ogunnus( life cycle stages duration, egg laying number and incubation time, feeding habits, respiration, production, and consumption rates, vertical migration, etc.) and its role in the Kinneret food web were previously studied on during short terms cases. Temporal (1970-1990) fluctuations accompanied by ecological considerations of the demographic parameters are presented here. Numerical averages (1970-1990) indicates 56% reduction, between recorded Nauplii and adults. The majority of the decline is due to copepodites. This reduction is probably due mostly to fish predation. Seasonal (monthly) changes indicates significant increase of nauplii, and copepodites from January to December whilst the density of adults increased seasonally during the 1970`s and dropped during the 1980`s. These upward trends are probably due to normal temperature elevation. The decline of adults during the 1980`s was probably influenced by enhancement of fish predation pressure. Echo surveys show a multiannual rise of zooplanktivorous fish populations (bleaks) size from 1987 to 2005. Annual significant density decline during 1970-1990 of nauplii, copepodites and adults as well as total number of eggs was documented. Consequently, the eggs per female value did not change. Density fluctuations of adult copepods (predator) and cladocerans (potential prey) were identical as a result of mutual predator with similar prey preferences. Significant impact of predator copepods on cladocerans is therefore eliminated. Life span of adults is longer than that of nauplii and copepodites together. Consequently, if longevity is the dominant impact on densities of copepodites 3-5 and adults, the adult longer span make their accumulated density higher. Due to the bigger size of adults (0.8-1.2 mm) than copepodites (0.3-0.7 mm) and nauplii (0.1-0.3 mm) they are more vulnerable to visual predator fishes but their advantageous high speed swimming behavior equipped them with a higher escape ability from filter feeding fishes. The small nauplii and young copepodites are less visible


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and therefore better protected from visual feeders fishes (Bleaks, fingerlings) but more susceptible to filter feeders fish (tilapias). The higher densities of all demographic stages in spring-summer-fall months is resulted by temperature elevation which make development time shorter and metabolic rates (respiration, consumption, production) higher. In spite of long term elevation trend of temperature, densities declined as a result of intensification of fish predation.

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Documents

Meeting of the SIL Plankton Ecology Group (PEG 2012) · Abstracts of the SIL Plankton Ecology Group. Mexico City, Mexico,12-18 February, 2012 _____ 2 Vertical flux of phytoplankton