Community structure of phytoplankton, zooplankton and macroinvertebrates in restored and natural aquatic habitats of

Danube Delta – a preliminary assessment

Orhan Ibram – aquatic macroinvertebratesLiliana Török - phytoplanktonMihaela Tudor - zooplankton

Hidrobiology LaboratoryDanube Delta National Institute

Channels blocking

Babina area (satellite images)

1993 1996

1993 1996

Fortuna Lake

Danube

--Former polder for forestryFormer polder for forestry

Selected natural lakes

Isac

Uzlina

Cuibul cu Lebede

Images from GoogleEarth

Chaneging connectivity and lake typology

Type 2 Type 1 Type 3

clay sand-silt organic

River

OOsterberg W., Staras M., Bogdan L., Buijise A. D., Constantinescu A., Coops H., Hanganu J., Ibelings B. W., Menting G. A. M., Navodaru I. and Torok L. (2000) “Ecological gradients in the Danube Delta; present state and man-induced changes”. RIZA the Netherlands, Danube Delta National Institute Romania and Danube Delta Biosphere Reserve Authority Romania. RIZA rapport nr. 2000.015

Type 1 lakes

•Turbid lakes with high biomass of phytoplankton and zooplankton and a low cover of aquatic vegetation and filamentous algae;

•The abundance of cyanobacteria and cladocera is relatively high;

•These lakes tend to be deep and large with sand-silt substrate and a low variation in waterdepth

Type 2 lakes

•Clear lakes with a high abundance of the Potamogeton trichoides community, often with filamentous algae;

•In these lakes phyto- and zooplankton biomass and turbidity are low;

•These lakes tend to have a high seasonal variation in waterdepth and a low cumulative residence time

Type 3 lakes

•Clear lakes, often with filamentous alge;

•Phyto- and zooplankton biomass are low;

•Shallow and small with organic substrate;

•High cumulative residence time

Evolution of phytoplankton diversity in Babina and Fortuna areas

Analiza comparativă abundenţei numerice vs. diversitate fitoplanctonică în Ostrovul Babina (2003 & 2010)

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nr.ind./l

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4H' (div.)

2003 2010 H'/2003 H'/2010

•The abundance of the phytoplankton found shows that diatoms constitute a significant component of the community;

•The analyis of the saprobic status of the recorded species revealed a predominance of meso-saprobous algae species

Analiza comparativă a abundenţei numerice relative vs. diversitate fitoplanctonică în incinta Fortuna (2006 & 2010)

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H' (div.)

2006 2010 H'/2006 H'/2010

Phytoplankton in natural and restored areas

-There is no significant differences between phytoplankton development in natural lakes compared with restored areas;-In Isac lake high values of chl “a” are not given by blooms of cyanobacteria which are in general responsible for water degradation

Evolution of zooplankton diversity in Babina

•There is a significant increasing of the species number since the polder was flooded (1994), more interesting in the last 4 years when the species number almost get doubled;• The dominant genus was Brachionus spp, represented by 6 taxa. After flooding the polder many species that are indicators of permanent waters occurred. The constant forms that occur every year are: Chydoridae (cladocera), Cyclopidae (copepoda) and Brachionidae (rotifera).

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1993 1994 …… 1997 1998 1999 2000 2001 …… 2003 …… 2010

nr.s

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Evolution of zooplankton diversity in BabinaThe frecquency of rotifers families w ithin Babina Island

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1997 1998 1999 2000 2001

Philodinidae

Collothecidae

Trichocercidae

Testudinellidae

Synchaetidae

Lecanidae

Habrotrochidae

Dicranophoridae

Notommatidae

Asplachnidae

Gastropodidae

Lindiidae

Adinetidae

Brachionidae

• The most abundant taxonomic groups recorded until 2010 were the rotifer species. The rotifers community across all channels, lake and outlet was overwhelmingly dominated by Brachionus spp. (>50%). These species are found generally in eutrophic waters (Berzins and Pejler, 1989). • In terms of density, small herbivorous rotifers (e.g. Keratella sp. and Aschomorpha sp.) are the most abundant in the first year after flooding, these species being characteristic for eutrophic waters (Premazzi et al., 1992).

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Cladocera Copepoda Rotifera

Evolution of zooplankton diversity in Fortuna

Zooplankton structure reveals low abunance of Cladocera and dominance of Rotifera group with a low overall abundance;

Both species number and no of individuals/liter has decreased

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Zooplankton in natural and restored areasAbundance distribution of zooplanckton in natural lakes

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Isac Uzlina Cuibul cu Lebede

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Cladocera Copepoda Rotifera

Abundance of zooplankton in the "lake" of island Babina and Fortuna polder

0246

8101214

Babina Fortuna

no.in

d/l

Cladocera Copepoda Rotifera

•Community structure - no difference between natural and restored areas; both types are dominated by copepods;

•Differences are related to the abundance; natural lakes with higher abundances than the restored ones.

•There is an “ inside group” difference in natural lakes separating Cuibul cu Lebede

Evolution of aquatic macroinvertebrates diversity in Babina (1996-2010)

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Hirudin

eeGas

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nr. specii

1996199719981999200020012010

• The polder waters may basically be classified in two faunistic complexes:1. Running waters-hard bottom-lacking macrophytes;2. Stagnating-permanent or temporary waters;

The hard, loamy substrate next to the inlets is densely populated by specimens of the snail Lithogliphus naticoides in association with Viviparus sp. and Dikerogammarus villosus – freshwater shrimp-that hides into the woody litter;

The second group is composed mainly limnophylous species of worms, snails, crustacea, water mites and aquatic insects.

Evolution of aquatic macroinvertebrates diversity in Babina (1996-2010)

The species composition of the Gastropoda reflects some of the most important characteristics for the functioning of the rehabilitated wetlands of Babina. They live on dead macrophytes and thus contribute to the decomposition of plant biomass being also beneficial to the aerobic conditions in the water;

The fluctuation of the specimen number between the channels and lakes is not significant and may be neglected;

The species composition in the secondary channels is comparable to that of the main channel

Evolution of aquatic macroinvertebrates diversity in Fortuna (2006 & 2010)

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20062010

•Most frequent species are Bithynia tentaculata and Valvata naticina. The first one has broad habitat preferences inhabiting both running and standing water especialy in densely vegetated areas. The former prefers muddy or fine sand sediments and it is found mainly in on the shore of the channels with different degree of water velocity

Aquatic macroinvertebrates in natural and restored areasFive univariate measures are calculated for each spatial category. The number of species (S), total abundance (A), Margalef’s (d) species-richness measure, the Shannon-Wiener (H’) diversity index (to base loge), and Pielou’s evennes (J’). The formulae for the indices are as follows:

•Margalef’s d = (S-1)/Log (N) – where S is the number of species in the sample and N is the number of individuals;

•Shannon-Wiener H’ = -SUM(Pi x Log (Pi)) – where Pi is the proportion of species found in category I;

•Pielou’s evenness J’ = H’/Log (S) – derived from Shannon-Wiener to express the observed diversity as a proportion of the maximum possible diversity.

Aquatic macroinvertebrates in natural and restored areas

Margalef’s d gives a basic measure of species richness that makes some allowance for the numbers of the individuals present.

The magnitude of Shannon-Wiener may be affected by the distribution of the data, giving underestimates of diversity particularly with small sample sizes, and may also be affected by the number of categories.

Pielou’s J’ is used to express homogenity or relative diversity, the more similar the proportions of all species in the sample the closer J’ tends towards 1

Aquatic macroinvertebrates in natural and restored areas

A 1-way ANOVA test of differences between catchments showed three diversity indices were significantly different. (P<0.01) 0

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o. o

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cies

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Natural Restored

Mar

gale

f's (d

)

0.66

0.68

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0.72

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Natural Restored

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ou's

(J)

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Natural Restored

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Isac Uzlina Cuibul Babina Fortuna

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Conclusions

There is no significant differences between phytoplankton and zooplankton development in natural lakes compared with restored areas regarding community structure as opposed to aquatic macroinvertebrates;

Only one year of investigation is not sufficient; extending the analysis to other type of ecosystems like channels because dominate (as a proportion) the restored areas so the lakes are not the best representatives of these areas

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