Evaluation of modified Sphyrion tags for marking Caribbean spiny lobsters, Panulirus argusMeaghan C. Darcy1,2* and Carrollyn Cox.1 1Florida Fish and Wildlife Conservation Commission, Marathon, FL, USA; 2Marine, Earth, and Atmospheric Sciences Department, North Carolina State University, Raleigh, NC, USA.Mark-recapture studies have been traditionally employed in ecological and fisheries research to provide quantitative esti-mates on growth, movement, and mortality. Major assumptions of tagging studies are that the tags are permanent and do not effect the physiology and behavior of the animal. External tags have been used in long-term tagging studies and have been studied extensively, but have produced varying results for a variety of crustaceans. We conducted a laboratory study to investigate the suitability of modified Sphyrion tags by examining tag retention and comparing survival and growth rates of tagged and untagged P. argus. Male and female lobsters from two size classes, adults (76-90 mm CL) and large juveniles (61-75 mm CL), were used in the experiment. The lobsters were checked daily for evidence of mor-tality and ecdysis, and weekly for tag retention. The results show that 73 percent of all tagged individuals, experienced tag loss at the end of 24 weeks. No effect of sex or size is apparent. A three-percent difference in mortality was ob-served between tagged and untagged individuals. However tagged females of both size classes experienced higher rates of mortality than their untagged female conspecifics. The difference between mean total growth of tagged and untagged lobsters was 0.86mm, with untagged being larger. Females grew substantially less than males for both tagging treat-ments and grew less than their untagged female conspecifics. This study was conducted during mating season for lob-sters, which may have affected mortality and growth of female lobsters. The data indicates that the modified Sphyrion tag may not be suitable for long-term tagging studies or studies being conducted during reproductive periods for large ju-venile and adult lobsters.

The results of monitoring hard corals restored following the installation of telecommunication cables off Hollywood, FloridaDonald R. Deis.* 7785 Baymeadows Way, Suite 202, Jacksonville, FL 32256; telelphone (904) 367-8683; facsimile (904) 733-6621; e-mail drdeis@pbsj.com.The installation of five telecommunication cables at a cable station off Hollywood, Florida, caused the dislocation of 160 coral colonies, which were repaired. Monitoring of the repaired coral colonies, as required by the state and local environmental permits, has focused on survivorship. Survivorship has been taken to mean both successfully reattachment to the bottom and the effect of detachment and repair on the overall health of the colony, particularly in light of the decline of overall health of corals worldwide. A factorial experimental design was used to examine the effects of repair on the incidence of disease and mortality in the coral colonies. The experimental design also examined the potential differences between the reef systems, which occurred at different depths, and the five cables. Thirty repaired coral colonies and thirty reference coral colonies were examined at six months (February 2000), one year (August 2000) after repair, and two years (August 2001). ANOVA was used to understand the significance of any differences between the observations.All of the monitored, repaired corals have been found to be secured to the hard bottom reef surface by the repair process. Slightly more bleaching occurred in the one-year monitoring period; however, bleaching was not prevalent in the monitored corals during either period. No significant difference was found in the incidence of bleaching between the restored and the reference corals and between the second and third reefs. A significant difference was noted in the incidence of bleaching between the cables. Documented sources of recent mortality included serpulid (tube) worms, algae, and sponges. No significant difference in the percentage of recent damage was found between the restored and reference corals, between the second and third reefs, or between the five cables during this monitoring period. Year two results are being analyzed.

Food-web structure in introduced and native mangrove communities; a Hawaii-Puerto Rico comparisonA. W. J. Demopoulos,* L. A. Crawford, and C. R. Smith. Department of Oceanography, University of Hawaii, Honolulu, Hawaii, USA.Seven species of mangroves were introduced to the Hawaiian Islands from Florida in 1902 to reduce coastal erosion. At present, large portions of low-energy coastlines and stream banks are fringed by the red mangrove, Rhizophora mangle. This species has high dispersal capabilities, broad tolerance, and few natural enemies in Hawaii; as a consequence, the mangrove habitat appears to be expanding rapidly. Prior to the very recent invasion of mangroves, the intertidal zone of Hawaii essentially lacked vascular plants. The introduction of mangroves to intertidal habitats can dramatically alter a variety of ecologically important characteristics, e.g., rates of water flow, sedimentation, and detrital input. Mangroves produce large amounts of tannin-rich, nitrogen-poor detritus that may require special adaptations to digest. In Hawaii, animals are unlikely to have had time to adapt to this unique food source. Therefore, we hypothesized that mangrove detritus would be underutilized by detritivores in Hawaiian mangroves compared to native Puerto Rican mangrove habitats. We collected material from a variety of primary producers and consumers in Hawaii and Puerto Rico mangrove habitats and used stable carbon and nitrogen isotope analyses to evaluate potential carbon sources and trophic levels. Our results indicated that detrivores living within Hawaiian mangroves do not substantially utilize mangrove-derived material as a food source. Instead, a majority of the animals appeared to be a part of a particulate organic matter and benthic-green-algae based food web that included approximately 2 to 3 trophic levels. In contrast, several species from native Puerto Rican mangroves exhibited carbon isotopic values that overlapped with mangrove leaf material, indicating that mangrove detritus supports a small, but distinct detritivore community. Thus, in contrast to native mangrove habitats, Hawaiian mangroves do not appear to be supporting a productive, detritus-based community.

Linking habitat change and nutrient dynamics: comparison of food webs and nitrogen fluxes in burrowing shrimp- and oyster-dominated habitatsTheodore H. DeWitt* and Peter M. Eldridge. U.S. Environmental Protection Agency, Newport, OR 97365, USA.Endemic thalassinid burrowing shrimps are simultaneously dominant ecosystem engineering species and economic pests within Pacific estuaries. Dense populations of two shrimps (Neotrypaea californiensis and Upogebia pugettensis) commonly occupy >75% of intertidal and shallow subtidal tideflats. As a result of their burrowing, feeding, and burrow-irrigation, the shrimps modify the physical, chemical, and biotic structure of benthic habitats and aspects of overlying waters. These activities bring burrowing shrimp into conflict with oyster culture (Crassostrea gigas) because sediment excavated by the shrimps buries or smothers the oysters, and U. pugettensis may compete with C. gigas for food. Pesticide used to control burrowing shrimp on commercial oyster beds in Washington state creates a patchwork of shrimp-dominated and oyster-dominated habitats. Many impacts of pesticide and oyster culture on estuarine fauna have been characterized, but impacts to ecosystem functions have not been investigated. We used inverse-analysis-based food web models to examine how Upogebia- or oyster-dominated tideflats affect the flux of nitrogen between the tideflat and overlying water column. The food web models were parameterized using new and existing data on community structure, physiology, and feeding ecology of species found on un-farmed tideflats dominated by U. pugettensis and on commercial oyster beds. Separate food web models were constructed for four scenarios: Upogebia-dominated tideflats, and oyster beds sprayed with pesticide 1, 12, and 36-48 months before sampling. Two predictions generated by these models are that 1) Upogebia-dominated tideflats may have greater fluxes of nitrogen between the benthos and water column than oyster-dominated tideflats, and 2) Upogebia-dominated tideflats may sustain greater rates of in-situ primary production than oyster-dominated tideflats because of greater nutrient recycling.

Impact of iceberg scouring on benthic assemblages in the Southeastern Weddell Sea, AntarcticaJennifer Dijkstra1* and Julian Gutt.2 1Department of Zoology, University of New Hampshire, Spaulding Life Sciences, 46 College Road, Durham, NH 03824, USA; 2Alfred-Wegener Institute for Polar and Marine Research, Columbusstrasse, Postfach 120161, D-27515 Bremerhaven, Germany.Icebergs in the Southeastern Weddell Sea scour the sea floor resulting in deep gouges and/or slumping in the sediment. Until recently, the impact of iceberg scouring on benthic communities was difficult if not impossible to determine due to the lack of a eulittoral zone which prohibited diving. With the advent of the remotely operated vehicle, studies examining the effect of iceberg scouring in this area became feasible. These recent studies demonstrated that scouring of the sea floor resulted in complete destruction of benthic assemblages and created vacant areas that are re-colonized by mobile and sessile pioneer species. The aim of this study was to quantify and compare distinct stages of iceberg scoured assemblages. This was done to determine differences in compositional and structural components of succession. Images taken from a remotely operated vehicle were used to quantify succession in ice scoured regions. Approximately 1500 m2 of videotaped bands from three separate sites were analyzed for structural and compositional components of successional stages. The results of this study showed that total number of individuals, species richness and evenness increased from freshly scoured areas to undisturbed assemblages. Sessile suspension feeders such as hexactinellid sponges and colonial ascidians occupied the majority of space in undisturbed areas, whereas gorgonians dominated newly re-colonized areas. Also, the result of a multi-dimensional scaling plot revealed a subtle gradation in community composition between different stages in re-colonization in which differences between sites at the same successional stage are attributed to the proximity of the stations to the ice-shelf.

Community structure in mussel beds at Logatchev, a deep-sea hydrothermal vent on the Mid-Atlantic RidgeM. B. Doerries* and C. L. Van Dover. Department of Biology, College of William and Mary, Williamsburg, VA 23187, USA; e-mail mbdoer@wm.edu.Chemosynthetic deep-sea communities of the Mid-Atlantic Ridge have been described as having two biogeographic provinces based on preliminary species lists and the distribution of two vent mussel species: Bathymodiolus azoricus in the north (Menez Gwen, Lucky Strike, Rainbow) and B. puteoserpentis in the south (Snake Pit, Logatchev). As a part of a quantitative study of species composition and community structure at comparable habitats across these sites, replicate samples of mussel-bed fauna were collected at Logatchev, the southern-most known site on the Mid-Atlantic Ridge. Preliminary visual observations indicate Logatchev has a high biomass, dominated by ophuroids, compared to other vent sites on the Mid-Atlantic Ridge. Further analysis of samples will estimate species richness, evenness and composition, aiding our ability to define biogeographic provinces on the Mid-Atlantic Ridge. Through quantitative and comparative methods of sampling and examining habitats common to most vents, the information collected from Logatchev and other sites will contribute to our understanding of the underlying processes that lead to the development of chemosynthetic biogeographic zones, their ecological and geographical constraints, and the processes leading to divergent community structures.

The interaction of spatial variation and post-settlement density dependence in the intertidal porcelain crab, Petrolisthes cinctipesMegan J. Donahue.* Section of Evolution & Ecology, University of California, Davis.In marine populations, variation in larval supply and post-settlement density dependence interact to determine benthic population size and spatial distribution. Petrolisthes cinctipes is a widely-distributed, intertidal porcelain crab with planktotrophic larvae. Like many marine organisms with planktonic larvae, P. cinctipes exhibits high spatial variation in larval supply and local adult density. In this study, I demonstrate two sources of post-settlement density dependence in Petrolisthes cinctipes: gregarious settlement and intraspecific competition. Using density manipulation experiments in the field, I quantify the positive influence of local adult density on settlement rate. Using field and laboratory experiments, I demonstrate the negative effect of density on individual growth rate in all but the largest size class of P. cinctipes. Finally, I offer a framework for understanding how spatial variation in larval supply and local density will interact with these sources of density dependence.

Sponge dynamics in nearshore hard-bottom communities of the Florida KeysScott Donahue* and Mark J. Butler IV. Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA.Sponges, octocorals, and stony corals are the dominant sessile fauna within hard-bottom communities in Florida Bay, FL (USA). The sponge component of these communities has been cyclically decimated from as early as 1844, but most recently experienced a mass die-off of nearly all sponge species in south-central Florida Bay in 1991 and 1992, apparently in association with phytoplankton blooms. Our sponge transplant studies over the past two years suggest that conditions in these formerly impacted areas have recovered sufficiently to permit the survival and growth of several sponge species. However, continued episodic blooms and the proposed restoration of the Everglades hydroperiod have the potential to impact the sponge community in these areas in the future. Therefore, we are investigating the potential role of several sponge taxa in the maintenance of hard-bottom habitat via their influence on local hydrodynamics and the recruitment of sponges and other sessile fauna. Our preliminary evidence suggests that large physical structures such as sponges enhance scouring of the bottom adjacent to them, with potential impacts on local sediment depth and larval settlement. Thus, we are currently examining the recruitment of sessile invertebrates on artificial substrates placed at varying distances around different sponge taxa.

Possible sources for symbiont variation within the genus Aiptasia over time and spaceMeredith Dorner,* Scott Santos, Gemma May, and Mary Alice Coffroth. Buffalo Undersea Reef Research, Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY 14260, USA; telephone (716) 645-2718.Sea anemones within the genus Aiptasia are distributed worldwide and typically harbor symbiotic dinoflagellates. Aiptasia collected from Japan (A. pulchella), Hawaii (A. pulchella), Eilat (A. pulchella), Bermuda (A. pallida), and Puerto Rico (A. pallida) all harbored zooxanthellae belonging to Symbiodinium clade B, as determined by restriction fragment length polymorphism of nuclear small subunit (n18S)-rDNA. In contrast, A. pallida from the Florida Keys usually host Symbiodinium belonging to clade A. Sampling in Florida in the winter has revealed some individuals which possess Symbiodinium from clades A and B. Two hypotheses are proposed to explain these observations: (1) The Aiptasia sp. found in the Florida Keys are a different species than those found in other areas sampled. (2) The cladal variation observed among the Florida Keys Aiptasi sp. is in response to environmental variation. An ongoing study is evaluating the influence of the environment on this symbiosis by sampling Aiptasia sp. from the Florida Keys each month as well as conducting experiments to determine the effects of light and temperature on zooxanthella clade.

Hitchhiking hydroids: assessing the relationship between the coquina clams Donax and the hydroid Lovenella gracilisJoanne R. Dougherty* and Michael P. Russell. Department of Biology, Villanova University, Villanova, PA 19085, USA.The coquina clams in the genus Donax are dominant members of the infaunal community of high-energy sandy beaches. Donax are often found in association with an epibiotic hydroid, Lovenella gracilis. This tufted brown hydroid uses the external posterior end of living clams as a substrate. The significance of the relationship between the clam and the hydroid has not been studied extensively, however some workers suggest that the L. gracilis forms a symbiotic relationship with the clam. I plan to investigate the effect of L. gracilis on the population biology, life history, and distribution of Donax by quantifying the effect of the hydroid on clam growth and rates of predation by gastropods. I will also document the seasonal variation in the association of the hydroid with Donax over the next year. Preliminary field data suggest that there is a size-specific relationship between the clam and the hydroid in that larger clams are more likely to have hydroids, however, the hydroid has been observed on recently settled juveniles as small as 2 mm in length.

Dispersal and recruitment in terrestrial versus marine environments: the benthos is not just an underwater landscapeC. Ashton Drew* and David B. Eggleston. North Carolina State University, Marine Earth & Atmospheric Sciences, Jordan Hall Box 8208, Raleigh, NC 27695, USA.Existing landscape ecology theory has primarily been developed within terrestrial systems and has not been adequately tested in marine environments. The assumptions and methods appropriate for modeling terrestrial systems might not apply in marine environments. While terrestrial organisms generally move through a landscape, most marine organisms can utilize hydrodynamic currents to disperse over a landscape, requiring a three-dimensional conceptualization of movement patterns. We use a cellular automata model to compare recruitment success resulting from various terrestrial versus marine dispersal strategies within patchy environments. We likewise evaluate how recruitment success of a given dispersal strategy responds to landscape changes. The modeled dispersal strategies are: (1) terrestrial, where an individual may move in any direction based upon habitat preference; (2) passive marine, where an individual cannot move against or perpendicular to the current; and (3) active marine, where an individual can move in any direction but the current significantly biases potential movement. A highly successful recruitment event has a high number of settlers in suitable habitat (maximum survival) and results in a broad spatial extent of recruit distribution across the landscape (spreading risks associated with random environmental perturbations). We conclude: (1) differences in individual dispersal strategy can lead to significant differences in recruitment success within similar landscapes, and (2) the dispersal patterns and overall recruitment success of each strategy responds predictably to changes in landscape structure. We conclude with a presentation of how these modeled results can be combined with remotely sensed landscape mosaics to predict recruitment success marine species with varying dispersal capabilities, including: Nassau grouper (Epinephelus striatus), Caribbean spiny lobster (Panularis argus), Queen conch (Strombus gigas).

Assessing changes in photosynthetic parameters in response to varying environmental stimuli using chlorophyll a fluorescenceMark D. Driscoll,1* Florence I. M. Thomas,1 and Kevin S. Beach.2 1Department of Biology, University of South Florida, 4202 E. Fowler Ave. Tampa, FL 33602, USA; 2Department of Biology, University of Tampa, 401 W. Kennedy Blvd, Tampa, FL 33606, USA.In recent years, several new technologies have been developed that have the potential to drastically change the way eco-physiologists carrying out experiments in situ and in the laboratory. The use of chlorophyll fluorescence has emerged as an important tool in the investigation of photosynthetic pathways. Measurements of specific photosynthetic parameters (e.g. quantum yield, saturation irradiance [Ik], inhibition irradiance [I]) have been used to evaluate changes in photosystem configuration and operation in response to variable environmental conditions in terrestrial and marine (e.g. seagrasses, corals, macroalgae) systems. These studies have primarily focused on determining how the photosystem responds to changes in light regime. In addition to light, it has been shown that changes in the rate of chemical diffusion through the benthic boundary layer can affect primary production. The thickness of this boundary layer is reduced in high velocity flow, and increased at low velocities, effectively changing the nutrient flux to the organisms surface in response to hydrodynamic variations (e.g. tides, waves). Using a diving PAM (pulse amplitude modulated) fluorometer, we tested the photosynthetic responses of macroalgae (Caulerpa racemosa, and C. sertulariodes) to changes in hydrodynamic regime and irradiance in the laboratory and field. The use of chlorophyll a fluorescence in these experiments allows for a direct measure of photosystem response with a minimum interruption of water flow or blockage of irradiance. Changes in photochemical (Pq) and non-photochemical (NPQ) quenching, saturation irradiance (Ik), inhibition irradiance (I) and the maximum electron transport rate (Pmax) were measured. Results indicate that photosynthetic responses vary with changes in physical and environmental regimes.

The when, where and why of alternative states in rocky intertidal landscapesSteve Dudgeon,1* Christin Slaughter,1 and Peter S. Petraitis.2 1Department of Biology, California State University, Northridge, CA 91330-8303, USA; 2Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.The mid intertidal zone of rocky shores in the Gulf of Maine is characterized by 4 conspicuous taxa, Ascophyllum nodosum, Mytilus edulis, Semibalanus balanoides and Fucus vesiculosus, that serve as foundation species of the respective assemblages that each dominates. At sites between the extremes of water motion on rocky shores, either barnacle-mussel beds or stands of rockweeds can dominate the same physical environment and may represent alternative states. Our empirical evidence of spatial scale dependent patterns of recruitment and mortality supports this hypothesis, but variability in succession among sites suggests that the potential for alternative states may be site-specific. To understand why at some sites communities can switch, but elsewhere cannot, we have developed a spatially-implicit community-level model consisting of these 4 species. Model parameters are based on empirical data taken from populations of each species in the Gulf of Maine or Nova Scotia, including ours on scale-dependent recruitment and mortality. The model assumes an area of 500m2 and runs on a per month basis over several years following an ice scour event. As Petraitis and Latham (1999) hypothesized, a switch between states requires scale dependent rates of processes: without it, an established assemblage is resilient and maintains dominance even following clearings >100m2(i.e., site-specific factors determine outcome). Alternative states occur when recruitment and mortality are spatial scale dependent. However, Ascophyllum resists invasion and is stable following clearings up to 12.25 m2 in area (4 m in diameter). In simulations of clearings between 4 and 12 m in diameter a switch to barnacles and Fucus vesiculosus occurs, in agreement with our empirical data on Swans Island over the past 5 years. Successful invasion by mussels requires clearings ≥12 m in diameter. The model accommodates both the alternative state and site-specific outcomes observed at different locations on New England rocky shores.

Biodiversity and ecosystem function: the consumer connectionJ. E. Duffy,* J. P. Richardson, and K. France. School of Marine Science/VIMS, College of William & Mary, Gloucester Point, VA 23062-1346, USA.Proposed links between biodiversity and ecosystem processes have generated intense interest and controversy in recent years. Most empirical studies have focused on grassland plants and aquatic microbial systems, with little attention to potential consequences of changing animal diversity. Theory suggests that changing diversity in multi-level food webs can have effects on ecosystem structure and function qualitatively different than those mediated by plants. We are addressing consequences of changing consumer diversity and food web architecture experimentally using eelgrass-beds as a model system. Here we report results from two mesocosm experiments (see Paul Richardson’s poster for tests of mesocosm realism), one in summer and one in fall. The first exposed eelgrass to each of six mesograzer species singly, in random combinations of three, and to all six species together. Epiphyte accumulation, total benthic biomass, benthic community structure, and grazer secondary production differed strongly among grazer species, and total grazer impact was correlated with grazer diversity. The diversity trend resulted from a sampling effect, however, i.e., the most diverse grazer treatments were more likely to include the most voracious grazer species. In the second experiment (fall), we measured impacts of predators (juvenile blue crabs) on food webs varying in diversity at the intermediate (grazer) trophic level. Grazer treatments differed in susceptibility to predation and, thus, in their damping effect on cascading impacts of crabs on plants (see Melanie Spring’s talk for details of the cascade). Comparison of the two experiments and field abundance patterns suggests that more diverse grazer assemblages exert more consistent pressure on plants due to seasonal asynchrony in population cycles among grazer species. Evaluating impacts of biodiversity loss on ecosystem function requires a more systematic expansion of the scope of current experimental research to multi-level food webs.

Measuring microphytobenthic production and consumption using a spectrophotometric methodA. L. Dunsmuir* and J. Cebrian. Dauphin Island Sea Lab, 101 Bienville Blvd, Dauphin Island, AL 36528, USA.Measuring oxygen production and/or consumption by microphytobenthic communities is often a difficult task. These measurements are normally taken in-situ or in laboratory incubation chambers with an oxygen probe, which normally requires significant water movement to be accurate. This can be achieved by using either a stirring probe or magnetic stirrers within the chambers. The need for stirring often incurs significant cost. Moreover, it can result in substantial bias due to experimental error. A new spectrophotometric method to measure oxygen production by phytoplankton has recently been developed. The method is fast, precise and effective. It also performs over a wide range of concentrations, from anoxic to over-saturated environments, and it has been shown to out-perform classical techniques such as the Winkler titration. However, the new method has yet to be applied to microphytobenthic communities. Here, we use the new method to derive in-situ measurements of oxygen production and consumption by temperate microalgal communities, and evaluate its performance in relation to measurements taken with an oxygen sensor and stirring probe. Our study confirms the new method is faster, more efficient and more sensitive.

Variation in heat shock protein expression during queen conch larval metamorphosisAngela Duque,1* Hayden Long,1,2* Melanie Caldwell,1* and Anne Boettcher.1 1Department of Biological Sciences, University of South Alabama, Mobile, AL, USA; 2Neuroscience Program and Department of Psychology, Tulane University, New Orleans, LA, USAHeat stress is known to induce larval metamorphosis in a variety of marine invertebrates, including the queen conch, Strombus gigas. Although many of the cellular responses triggered by this induction are not well understood, increases in the expression of a number of proteins are thought to be associated with this process. In the current study, the role of heat shock proteins (HSP’s) in the induction of queen conch metamorphosis was examined. HSP’s are a family of proteins named for their molecular sizes, which range from 20-100 kDa. They are intracellular molecular chaperones that facilitate protein folding and assembly. Known to be produced in response to environmental stress, HSP’s are also involved in the routine folding and transport of cellular proteins under natural conditions. Changes in the expression of HSP 90, HSP 70, and HSP 60 during queen conch metamorphosis were compared between heat-induced larvae and larvae treated with a natural inducer of metamorphosis, an extract of the red alga Laurencia poitei. After exposure to heat stress or the algal inducer, larvae were homogenized in sample buffer, proteins separated by SDS-polyacrylamide gel electrophoresis and analyzed by immunoblotting with antibodies specific to the three HSP’s. Induction of metamorphosis was coupled to increases in the expression of HSP’s. However, the patterns for heat-treated larvae were different from those for larvae exposed to the algal extract, as increases in expression occurred earlier in the induction process for the heat-stressed larvae. These results suggest distinct roles for HSP’s during normal conch metamorphosis and in response to stressful environmental conditions.

Is shell color polymorphism in Littorina obtusata influenced by selective predation by crabs?Lauralyn Dyer.* Department of Zoology, University of New Hampshire, Durham, NH 03824, USA; e-mail ldyer@cisunix.unh.edu.Littorina obtusata is an intertidal, herbivorous snail common to the New Hampshire coast that is polymorphic for shell color. In many species cryptic coloration has been shown to increase fitness by reducing predation. In order to test if predation is influencing color distribution in L. obtusata I conducted feeding experiments. The primary predator of L. obtusata in NH is the invasive green crab, Carcinus maenas. Although C. maenas primarily searches for prey using chemoreception, many researches have questioned their predatory role in shaping a given L. obtusata population in regards to shell color. I also used the invasive Asian shore crab, Hemigrapsus sanguineus, which recently has been found in NH. I hypothesized that yellow (non-cryptic) snails on an algal background would be selected by the two crab species more than brown/olive (cryptic) snails. To determine if crabs had a preference for shell color, crabs were offered equal numbers of yellow and brown/olive snails under light and dark conditions. Neither crab species showed a significant preference for shell color in either light treatment. However, H. sanguineus ate significantly more total snails in the light condition than the dark, whereas C. maenas showed no significant difference between light treatments in number of snails eaten. These results indicate that C. maenas is not likely responsible for shaping the shell color frequency of L. obtusata, and that H. sanguineus will not affect color frequency as it continues to invade the New Hampshire coastline. However, as the two crab species compete for resources it is possible that C. maenas will feed more at night, while H. sanguineus will feed during the day.

Modeling the effects of chronic increases in seawater temperature on the population biology of reef coralsPeter J. Edmunds.* Department of Biology, California State University, Northridge, CA 91330, USA.It is likely that the increasing seawater temperatures associated with global warming will have a substantial effect on coral reefs, arguably with the most serious consequences for symbiotic corals. Although much is known about the roles of high temperatures in coral bleaching, little is known about the effects on entire coral populations. The purpose of this study was to test the effects of elevated temperatures on coral growth, and to use size-based demographic models to explore the population consequences of these effects. The effects of temperature on growth were assessed using sympatric branching corals from the southern GBR—Seriatopora hystrix, S. caliendrum and P. damicornis—and treatments consisting of three-day exposures to one of 4 temperatures (up to ambient +6°C). Temperature significantly affected growth in a parabolic relationship, but there were no significant differences among species, and no temperature x species interaction. Together with empirical Leslie Matrix models, these relationships were used to project population structures under different scenarios of rising seawater temperature. The results suggest that existing inter-specific differences in population structure will be maintained in a future environment 4°C warmer than present. Although one aspect of increasing seawater temperature may have only small effects on coral populations, the role of short-term thermal “spikes” is unknown.

The interacting effects of humans and nature on marine populations: hurricanes and fishing contribute to population decline in the blue crabDavid B. Eggleston,* L. E. Etherington, and E. G. Johnson. Department of Marine, Earth, and Atmospheric Science, North Carolina State University, Raleigh, NC 27695-8208, USA.During 1999-2001 we identified a concurrent and precipitous decline in abundance, spawning stock, young-of-the-year, and postlarval stages of the blue crab (Callinectes sapidus) in Pamlico Sound, NC. Specifically, adult abundance declined by 74%, spawning stock by 75%, young-of-the-year (YOY) by 63%, and postlarvae by 71%. Fisheries-dependent and -independent data suggests that the decline was due to the interacting effects of three sequential hurricanes in fall, 1999 (Dennis, Floyd, Irene), which caused 50- to 500-year flooding in the Pamlico Sound watershed, and intense localized fishing pressure. Floodwaters displaced three-fourths of the volume of the Sound which led to a massive relocation of crabs from up-estuary tributaries to the central portion of the Sound where salinities were higher. Crabs that were concentrated in the Sound were subject to intense fishing where catch rates tripled compared to average catch. Concurrently, postlarval supply to the Sound was extremely high during fall 1999 as a consequence of hurricane wind-driven transport, yet there was apparent recruitment failure in 1999. Our data suggests that recruitment failure was due, in part, to disruption of secondary, pelagic dispersal of early juvenile crabs to the Sound by hurricane floodwaters. We suggest that the concurrent and precipitous decline in NC’s blue crab population beginning in 1999-2000 was due to overfishing localized, high concentrations of crabs displaced by hurricane floodwaters and recruitment failure of YOY. A strong stock-recruitment relationship for the blue crab in NC indicates an urgent need to conserve spawning stock for long-term population persistence.

Development of horseshoe crab embryos and larvae in a hypersaline environmentG. S. Ehlinger* and R. A. Tankersley. Department of Biological Sciences, Florida Institute of Technology, 150 W. University Blvd., Melbourne, FL 32901, USA.The American horseshoe crab, Limulus polyphemus, typically inhabits estuarine systems with salinities ranging from 5–34 psu. During spawning, females lay their eggs beneath the sand in the high intertidal zone. Previous studies indicate that the optimal temperatures and salinities for embryonic and larval development are 25–30°C and 20–30 psu, respectively. While embryos are able to develop at salinities < 40 psu, tolerance of higher salinities has not been investigated. Studies of the L. polyphemus population in the Indian River Lagoon (IRL), Florida indicate the population may be declining and that larval development and survival may be impacted by elevated temperatures and salinities that occur during the spawning period. The objectives of this study were (1) to determine the effect of high temperatures and salinities on the survivorship, hatching rate and embryonic development of L. polyphemus and (2) to determine the effects of changes in external salinity on the osmotic concentration of the perivitelline fluid. Artificially fertilized eggs were raised at five salinity (30-60 psu) and temperature (25-40°C) combinations. Both embryos and larvae successfully developed, hatched and molted at salinities as high as 60 psu. However, embryonic development and hatching failed at temperature > 35°C. To determine if developing embryos are buffered from changes in external salinity by the regulation of the perivitelline fluid, we exposed eggs reared at 30 psu to salinities ranging from 5-90 psu and measured the osmotic concentration over a six hour period. Under all test conditions, the osmotic concentration of the perivitelline fluid conformed to the surrounding media. These results indicate that high temperature and salinity conditions influenced the rate of horseshoe crab development, yet, had a limited effect on survivorship and do not account for the low abundance of larvae in the IRL.

Predation by Great Black-backed Gulls (Larus marinus) on crabs in the New England rocky intertidal and shallow subtidalJulie C. Ellis,1* Walter Chen,2 and Myra Shulman.2 1Brown University, Department of Ecology and Evolutionary Biology, Providence, RI, USA; 2Cornell University, Department of Ecology and Evolutionary Biology, Ithaca, NY, USA.The intertidal is primarily a marine community; nearly all its inhabitants are marine in origin, and many have distributions that extend into the subtidal. However, terrestrial consumers may exploit the intertidal during low tides; such opportunistic foragers include birds and mammals. These consumers have the potential to influence abundances and upper distributional limits of prey species. Two species of gulls (Great Black-backed Gulls and Herring Gulls) nest on Appledore Island, in the Gulf of Maine; both forage in the intertidal. In this study, we focused on the predatory effects of Great Black-backed Gulls (Larus marinus) on intertidal populations. We examined: 1) temporal and spatial patterns in gull foraging in the intertidal, 2) rates of predation on three species of crab: Cancer borealis, C. irroratus, and Carcinus maenas, and 3) effects of predation on crab distribution. C. borealis was preyed upon far more often than Carcinus and C. irroratus, both in absolute numbers and relative to their abundance within the foraging range of the gulls. Per capita predation rate of gulls on crabs during a single tidal cycle per km of shoreline was 72.7 and 83.1 at the two study sites; the daily predation rate on C. borealis represented 36% to 50% of the standing crop found in the top stratum of the rocky subtidal. An experiment examining gull predation rates at 3 different tidal heights showed that 100% of tethered crabs were attacked at 1.0 m (relative to MLLW) and 0.0 m and only 40% or fewer attacked at –1.0 m. Both behavioral and experimental data indicate that despite their low densities, foraging Great Black-backed Gulls have a major impact on intertidal abundance and distribution of an important invertebrate predator, and may generate cascading effects on organisms at lower trophic levels.

Mangrove trimming: aesthetics at the expense of an ecosystem?William Ellis* and S. S. Bell. University of South Florida, Biology, Department, 4202 East Fowler Ave., Tampa, FL 33620, USA.Mangrove-dominated estuaries are highly productive coastal systems. The production of mangrove litter (i.e. leaves, wood, reproductive structures) and its subsequent consumption by higher trophic levels is said to represent a major pathway of energy flow. Consequently, damage to the mangrove canopy, where these vegetative structures areproduced, may impact ecosystem function.We examined the impacts of mangrove trimming, a common horticultural practice in Florida, on the canopy density and litter dynamics of mangrove stands in the Rookery Bay National Estuarine Research Reserve. Litterfall was quantified monthly over a twenty-seven month period in twelve study plots (18.0 x 14.0 m) distributed throughout the Reserve. Six of these plots were randomly selected to serve as trimming sites after the initial fifteen months of litter collection. Within these six plots, 50% of the foliage of each mangrove tree was excised and removed from the site. Canopy density loss and any subsequent recovery was quantified by an analysis of digitized canopy photographs taken at fixed points within each study plot several times over the course of this investigation. The monthly mass of ground litter and the mean rate of its decomposition within the plot types (i.e. trimmed mangroves vs. reference) were also measured.Mangrove trimming reduced canopy densities by an average of 30% with little evidence of recovery nineteen months after trimming was performed. Leaf litter production, the most severely impacted litter component, declined to one-half of that found in referenceplots. The amount of standing ground litter was not similarly impacted, as tidally driven imports and exports of litter obscured any corresponding changes in litter accumulation on the forest floor. Ground litter decomposition rates were higher in the reference plots than in the trimmed plots. These results indicate that mangrove trimming may considerably alter energy flow, particularly in systems with limited mangrove coverage.

Dietary preference for leaves of the red mangrove (Rhizophora mangle) as measured by leaf damage and by mangrove tree crab (Aratus pisonii) gut contentsAmy A. Erickson,* Mark Saltis, Susan S. Bell, and Clinton J. Dawes. Department of Biology, University of South Florida, Tampa, FL 33620-5200, USA.Herbivore consumption and diet preference often are assessed by determining the percent of damaged leaves in a given area. Another useful tool for the same analysis is examination of herbivore gut contents. Both techniques have been used in determining mangrove crab diets. While percent leaf damage indicates the extent to which plant populations are damaged or preferred, gut content analysis has distinct advantages. First, it allows an instantaneous versus a cumulative measure of consumption and preference. Second, it can be used to determine trophic status. Mangrove crabs considered as herbivores often supplement their diets with animal material, suggesting they are omnivores. This study compares the utility of one method against the other and examines whether comparable results are found for each. Mangrove tree crabs, Aratus pisonii, were sampled from stands of different mangrove species, around Tampa Bay, FL, during summer 2001. Stomach contents were dissected and classified to a number of categories. Species consumption and preference were determined by comparing relative numbers of mangrove stomata in gut contents and by determining the percent of damaged leaves in crab collection areas. Results suggest that both methods provide a relatively comparable estimate of preference. The instantaneous measures based on crab gut contents correspond to values of leaf damage found in the field, and the crab appears to consume predominantly mangrove but other food items as well.

Molecular phylogenetics of verongid sponges: utility of ITS-2 and 28S ribosomal DNA sequencesPatrick M. Erwin,* Kevin P. Bevis, and Robert W. Thacker. Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.Genomic DNA was extracted from 5 species representing 3 genera of sponges in the Order Verongida. The second internal transcribed spacer region (ITS-2) and a portion of the 28S ribosomal subunit of Poriferan nuclear ribosomal DNA (rDNA) were amplified by PCR from each species, yielding an approximately 600 bp product. After sequencing, 226 bp ITS-2 and 352 bp 28S were aligned and analyzed using PAUP*. Phylograms constructed from ITS-2, 28S, and the entire dataset were compared using maximum likelihood models to determine the phylogenetic resolution of each region of rDNA. More parsimony-informative characters were present in ITS-2 (n=73) than in 28S (n=26); thus, ITS-2 is a useful marker for intra-order comparisons. However, comparisons of ITS-2 to sponges in other orders were complicated by the great difficulty of alignment. The 28S subunit was more easily aligned among orders, indicating a greater number of conserved bases, but less useful within genera.

Movement of the green sea urchin, Strongylocentrotus droebachiensis, within three subtidal habitats of the Gulf of MaineKristine E. Faloon1* and C. E. Siddon.2 1Boston University Marine Program, Boston, MA, USA; 2Dept. of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA.The movements of individuals and populations are significant components of community structure and dynamics. Understanding factors that modify movement, especially in important consumer species, have implications for community composition, succession and species interactions. Habitat characteristics such as availability of refuges and alternative food sources may modify movement. We investigated the movement patterns of subtidal populations of the green sea urchin, Strongylocentrotus droebachiensis, within mussel beds, urchin barrens and algal dominated habitats of the Gulf of Maine, USA, to assess the impact of habitat characteristics on movement. A diffusion coefficient for tagged urchins was calculated and averaged across multiple sites within each habitat to quantify movement rates. Movement was significantly different in each habitat type with the highest rate of diffusion within mussel beds, followed by urchin barrens and algal beds. In barrens sites, with and without neighbor urchins present, movement was not affected by urchin density. These results demonstrate the effect habitat characteristics have on urchin movement and suggest that the movement of consumers may play an important role in structuring subtidal communities.

Diadema antillarum effects on benthic community structure in the Florida Keys National Marine Sanctuary (FKNMS): preliminary resultsCharles Fasano,1* Margaret Miller,1 Alina Szmant,2 and Nicole Fogarty.2 1NOAA-Fisheries, Southeast Fisheries Science Center, 75 Virginia Beach Dr., Miami, FL 33129, USA; 2University of North Carolina at Wilmington, CMS, 1 Marvin K. Moss Ln, Wilmington, NC 28409, USA.Following the die off of the sea urchin, Diadema antillarum, in the 1980’s thick turf and fleshy algae have proliferated on Caribbean reefs. We studied the effects of re-introducing moderate Diadema density on benthic community structure at Little Grecian Reef (FKNMS). Wild-caught adult Diadema were transplanted into fenced enclosures at a density of 7 m-2 (background Diadema density ~0 m-2). The density of Diadema in the enclosures was monitored periodically and declined over time. Four other areas served as controls (no Diadema, no enclosures). We estimated percent cover of bare surface, macroalgae (predominantly Dictyota sp.), Crustose Coralline Algae (CCA), and invertebrates (hard corals, sponges, Palythoa sp., and octocorals) using point counts of photographs taken at ca. bimonthly intervals. Initial conditions were quantified in May 2001, urchins were transplanted in July, and experimental effects were assessed after three, five, and seven months of urchin grazing. Biostatistical methods involved Multivariate Repeated Measures ANOVA. Initially, urchin and control treatments did not differ for all cover groups. After seven months, total macroalgae was lower in urchin treatments than controls but this predicted response was not evident for the first five months (Time*Treatment p=0.0057). CCA and bare substrate increased slightly but not significantly under Diadema grazing. Urchin grazing significantly depressed sponge cover and this effect increased over time (Time*Treatment p=0.033). Other invertebrate groups did not show significant treatment effect. Overall, grazing by a moderate density of Diadema antillarum had complex effects on benthic community structure.

Nutrient limitation of benthic macrophytes in the upper Florida Keys: an in-situ nutrient enrichment experimentMeredith Ferdie* and James W. Fourqurean. Southeast Environmental Research Center and Department of Biological Sciences, Florida International University, Miami, FL 33199, USA.South Florida contains some of the most expansive documented seagrass communities in the world. Stoichiometry of seagrass tissue from the upper Florida Keys suggest that benthic coastal communities are phosphorus (P) limited inshore and nitrogen (N) limited offshore. This spatial variability hypothesis of nutrient limitation is presently being tested with a one year in-situ sediment fertilization experiment. The objectives of this investigation are to determine the limiting nutrient for Thalassia testudinum growth and to assess the responses of inshore and offshore benthic communities to nutrient addition. Nutrient loading rates are based on current estimates of dominant nutrient sources in the Florida Keys. Each site (3 inshore, 3 offshore) consists of 4 treatments (N, P, N+P, control) with six replicates, for a total of 144 experimental plots. The following data from 6 months of nutrient enrichment are presented: seagrass productivity and leaf tissue C:N:P, sediment C:N:P, sediment chlorophyll a, and total epiphyte load. Results may be used to model changes that anthropogenic eutrophication may cause in the subtropical coastal marine waters of the upper Florida Keys.

Can whelks find food in flowing fluid?Matthew C. Ferner* and Marc J. Weissburg. School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA.Mobile consumers often forage by tracking chemical signals. Successful tracking behavior is particularly important in estuarine habitats where turbidity is high and hydrodynamic conditions can be variable. Compared to other abundant predators and scavengers in these habitats (e.g., blue crabs), whelks move relatively slowly and thus may employ sampling strategies and tracking behaviors that are different than those of faster foragers. Here we present results from a flume study of the tracking behavior of two sympatric species of whelks, Busycon carica and Busycotypus canaliculatus, which differ in morphology, activity level, and small-scale distribution. Each animal was randomly assigned to one of four flow velocities (1.5, 5, 10, or 15 cm/s) and exposed to either a control (seawater) or treatment (mussels soaked in seawater and then filtered). Significant differences were observed between species in terms of search behavior and frequency of tracking success. Busycotypus canaliculatus tracked faster and had a higher success rate at all velocities except 5 cm/s, at which both species were equally successful. The differential ability to follow chemical plumes in a range of flow velocities may cause these two species of whelks to forage more efficiently in different hydrodynamic environments. This suggests the potential for habitat partitioning that could reduce competition for food and may help to regulate community structure.

Fitness consequences of allorecognition-mediated agonistic interactions in the colonial hydroid Hydractinia [GM]David L. Ferrell.* Department of Biological Science, Florida State University, Tallahassee, FL 32306-1100, USA.Many clonal marine invertebrates possess competitor-induced structural defenses used for overgrowth or territorial purposes. The colonial hydroid Hydractinia [GM] utilizes an inducible defense when encountering conspecifics. My goal was to ascertain the consequences of agonistic interactions in H. [GM] for three primary fitness components: colony survival, growth rate, and reproductive effort. I investigated numerous encounters involving pairs of colonies differing in competitive ability established near or far from each other (resulting in interactions between small or large colonies, respectively). I collected five large colonies from St. Joseph Bay, FL, and established competitive contests between all pairwise combinations of colonies by attaching tissue explants from different colonies near (4 mm) or far (12 mm) from one another. All ten pairings were replicated five times at both distances, and five replicates of each colony were also established in the absence of competitors, as controls. Hydroid cultures were maintained in a single aquarium, and the survival, area covered (growth rate), and number of reproductive zooids (reproductive effort) of all colonies were recorded at 15, 30, 60, 80, and 90 days after establishment.Not surprisingly, interactions between small colonies generally imposed greater costs in terms of colony survival, growth rate, and reproductive effort. Also, competitors differed in colony survival, reproductive effort, and growth rate (though to a lesser degree). Superior competitors typically eliminated competitors in small-colony encounters, but in larger-colony interactions, only the most dominant competitors competitively excluded others. In such encounters between less dominant competitors, however, colonies exhibited increased reproductive effort and low mortality, although reduced growth was evident. In fact, in these instances reproductive effort was greater than that of control colonies established in the absence of competitors. I will discuss several implications of these results with regard to the life history evolution and ecology of H. [GM].

Spatial and temporal distribution of life history variants in the red alga, Mastocarpus papillatusJanna Fierst,* Janet Kübler, and Steve Dudgeon. California State University, NorthridgeNorthridge, CA 91330, USA.We investigated small scale spatial structure in Mastocarpus papillatus, a red alga with sexual and apomictic life history variants. Spatial structure and habitat partitioning can facilitate the coexistence of ecologically similar organisms, and in M. papillatus a large scale geographic spatial division is well documented. Variants of M. papillatus display geographic parthenogenesis where sexual fronds are common south of San Francisco Bay and apomicts dominate north of San Francisco Bay. Although geographic parthenogenesis in M. papillatus is well documented small scale spatial structure was not previously known due to the similar appearance of sexual and apomictic upright fronds. We investigated whether sexual and apomictic fronds differed in their spatial distribution by sampling for vertical differences in intertidal height and horizontal patchiness. Fronds were sampled when reproductive and cultured for life history. We found sexual variants were significantly aggregated at lower intertidal heights while apomicts were found throughout the intertidal range. Sexual fronds were strongly seasonal and reproduced October-December whereas apomictic fronds reproduced throughout the year. These results parallel the large scale geographic distribution with apomicts inhabiting marginal areas, and suggest dispersal capability may also facilitate geographic parthenogenesis.

Burrow ventilation by thalassinid shrimp from the northern Gulf of Mexico: mechanics of effluent plumes and effects on benthic communitiesChristopher Finelli.* Louisiana Universities Marine Consortium; 8124 Highway 56, Chauvin, LA 70344, USA; e-mail cfinelli@lumcon.edu.Thalassinid shrimp are common members of soft-sediment intertidal habitats along the Northern Gulf of Mexico where densities can reach 700 burrows m-2. Water contained within the burrow is enriched in inorganic nutrients (e.g. nitrogen, phosphorous, and silicate), and these nutrients may play an important role in benthic production if delivered to the surface sediment or overlying water column. However, very little is known about the temporal patterns of burrow ventilation or the fate of nutrients as they are pumped into the surface water. To address these issues, we are examining the biomechanics of burrow ventilation and effluent plume formation for several coastal species in the lab and field. The first phase of this research examines burrow morphology and temporal patterns of ventilation to parameterize later studies of effluent dispersal. Resin castings of burrows from two species, Callichirus major and C. islagrande, reveal elongated, narrow constrictions (chimneys) at the burrow outlet that are 2 to 3 times smaller in diameter than the burrow proper. These constrictions may act as a nozzle to increase exit velocity 4 to 9 times, and push effluent higher into the benthic boundary layer. Lab measurements show highly variable pumping patterns with bouts of burrow ventilation lasting seconds to minutes. Effluent velocities at the burrow exit can reach 12 cm s-1, with volume flows of 2 to 3 ml s-1. Shrimp in the lab were capable of pumping over 2 liters per day, even though ventilation was sporadic. Given observed burrow densities and estimated volume flow rates through the burrows, it is possible that 1400 L m-2 d-1 of burrow water is pumped into the overlying water column. We are currently investigating seasonal patterns of ventilation, the source of burrow water (i.e. porewater vs. surface water), and the effects of burrow effluent on benthic primary production.

Investigating the relative importance of shelter and landscape complexity in determining fish community structure within the northern Florida Keys National Marine SanctuaryGeremea P. Fioravanti* and John F. Valentine. Dauphin Island Sea Lab and the University of South Alabama, 101 Bienville Blvd. Dauphin Island, AL 36528, USA.Scientists and conservationists are increasingly concerned that the overfishing of marine consumers has caused significant alterations in the structure and function of marine ecosystems. Consequently, marine reserves are increasingly being utilized in an effort to restore commercially important higher-order consumers in tropical marine ecosystems. While it is true that the establishment of some marine reserves has led to the recovery of marine consumers, not all have been successful. Here I hypothesize that considering measures of reef structural complexity or landscape geometry can explain why marine reserves are not always successful. In this study, I used a randomly selected set of patch reefs located in the northern Florida Keys National Marine Sanctuary to determine which of these patch reef features were most important in controlling fish community structure. Based on visual censuses of fishes conducted on these patch reefs, community similarity varied greatly among sites. Using the chain method, we found a significant proportion of the variance in fish density and species richness could be explained by differences in reef structural complexity. In addition, I found that reef perimeter also played an important role, although it explained less of the observed variance than structural complexity, in determining fish community structure. These results indicate that landscape geometry is a potential factor in confounding the estimate of the recovery of higher order consumers in marine reserves.

RIDGE 2000: the next decade of innovative studies and discoveries at the mid-ocean ridgeChuck Fisher* and the RIDGE 2000 Steering Committee. Ridge 2000 Office, Department of Biology, Penn State University, 208 Mueller Lab Univerity Park, PA 16802, USA; e-mail ridge2000@psu.edu.Ridge 2000 is a new, National Science Foundation (NSF) sponsored research initiative that is looking for scientists and engineers. This program is community-based and promotes the interdisciplinary study of Earth’s oceanic spreading ridges. RIDGE 2000 is at the beginning of its anticipated 12-year duration with the general direction of the program already designed. However, there are still opportunities for participation in defining how these goals will be achieved. Investigators are needed to plan the program implementation and to carry out Ridge 2000 projects.Over the last 50 years, systematic observation and sampling of the world’s oceans have led to significant discoveries. This basic oceanographic research provided crucial evidence for the landmark theories of seafloor spreading and plate tectonics, and led to the discovery of ecosystems based on chemoautotrophy rather than photosynthesis. The RIDGE 2000 Program was conceived to promote an integrated approach towards the study of mid-ocean ridges. Outlined by community workshops over the past two years, it builds directly on the scientific and technological successes of the RIDGE Program. The scientific motivation for the RIDGE 2000 Program is encapsulated in the phrase “from mantle to microbes…” that expresses the inextricable linkages between processes of planetary renewal in the deep ocean and the origin, evolution and sustenance of life in the absence of sunlight.The RIDGE 2000 Science Plan aims for a comprehensive understanding of the relationships between the geological processes of plate spreading at mid-ocean ridges and the seafloor and sub-surface ecosystems that they support. Research under this program will be structured within an integrated, whole-system approach that will encompass a wide range of disciplines. Detailed studies of specific geographic areas will yield new insights into the connections among the biological, chemical and geological processes that are involved in crustal accretion and subsequent ridge crest processes.

Mussel mimics: an innovative way to show some intertidal mussels just aren't coolTara Fitzhenry,* Brian Helmuth, Kristi Gardner. University of South Carolina, Marine Science Program, Columbia SC, 29208, USA.Intertidal mussels (Mytilus californianus) live between the high and low tide lines of rocky coastlines of the northeastern Pacific, and are cyclically subjected to both aquatic and terrestrial environments. This alternating exposure can lead to rapid and sometimes extreme changes in body temperature, which in turn can have significant and even deadly physiological consequences. Because small temperature loggers have recently become available there are few long-term records of body temperature recorded under field conditions (Helmuth and Hofmann 2001). In order to estimate temperatures in the field we deployed a series of temperature loggers that were designed to thermally match live mussels (similar size, morphology and thermal inertia) at two sites in central Oregon (Boiler Bay and Strawberry Hill). Previous studies have shown that ecological and physiological patterns differ between these two sites, and may be a result of temperature effects, but this hypothesis has yet to be addressed. In controlled experiments, Mytilus californianus did not appear to gape to evaporately cool and therefore evaporation rates were not taken into account. Tests comparing these loggers to real mussels suggest that thermally-matched loggers recorded temperatures that are within a few degrees of real animals, and are considerably more accurate than unmodified loggers. Mussel logger temperatures at these sites reached maxima of 35° or greater, close to the predicted thermal tolerance of this species.To date, results indicate that temperature extremes at the Oregon site are quite high, and are comparable to temperatures recorded much farther south in California. Results suggest that temperature extremes might be slightly higher at the Strawberry Hill site than at Boiler Bay, in accordance with the pattern hypothesized by Dahlhoff and Menge (1996).

Life history observations of newly settled corals (Montastraea annularis species complex) over the first half-year post-settlementNicole Fogarty* and Alina M. Szmant. Center for Marine Science, University of North Carolina at Wilmington, 5600 Marvin K. Moss Ln, Wilmington NC 28409, USA.Few studies have documented survivorship patterns of newly settled corals and their interactions with surrounding organisms that are critical to recruitment success. Larvae of the Caribbean coral, Montastraea annularis, were settled in the laboratory on coral rubble or pre-conditioned clay and quarried limestone tiles. Observations began within a few days after settlement, but most were made beginning seven weeks later. Substrates were maintained either in running recirculating seawater (high light) or in shallow trays (low light) with water replaced weekly. Polyps were mapped, the substrate around them characterized, and spat observed. Of the 600+ initial polyps, 32% were on the 12 pieces of rubble, 26% on the 2 clay tiles , and 43% on the 2 limestone tiles. Settlement density was highest on the bottom surfaces of the limestone (8600/m2), and lowest on the tops and bottoms of the clay tiles (ca. 1700/m2). 73% of the larvae settled in aggregates of 2 to 3. More larvae settled on tile bottoms than tops (57 to 68 %). 41% settled < 1 cm from crustose coralline algae (CCA), 15% on CCA and 44% > 1cm from CCA patches. Zooxanthellae infection began one week after settlement; some polyps took 2 weeks to acquire them. Theca secretion was completed within 2 weeks. Skeletal and tissue fusion of aggregated polyps began 8-10 weeks post-settlement, with the exception of 1 cluster of 5, which fused within 1 month of settlement and began to produce extratentacular buds after 14 weeks. High mortality of spat in the well-lit seawater system was caused by algal overgrowth. Juvenile Diadema reduced algal overgrowth but sometimes ate the coral spat as well. Survivorship was greatest in the trays where at low light levels algal growth was considerably less. Overall survivorship after 5.5 months was 25%.

Marine macroecology: evidence from patterns in soft sediment fauna in the UKAndy Foggo.* Department of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK; e-mail Afoggo@Plymouth.ac.uk.Macroecology is the search for repeated, large-scale, statistically significant patterns in ecology such as latitudinal trends in diversity, or relationships between species’ abundance and frequency of site occupancy or geographical range size. It also represents an attempt to adopt a less reductionist approach to elucidating the underlying theoretical explanations for these patterns, and ultimately may provide the framework for predictive models and experimentation into these fundamental properties of assemblages.Macroecological studies predate the naming of this branch of Ecology by 30 years or so, but there has a recent surge of interest in macroecological patterns in the terrestrial ecology in the last decade. To date this surge has not been mirrored as strongly in marine ecology.Here I review some major macroecological patterns revealed in terrestrial studies, and use the extensive conservation database of the Marine Nature Conservation Review of the United Kingdom to search for replication of some of these patterns in British soft-sediment infauna. I draw some tentative conclusions on the use of such surveys in marine macroecological studies, and explore the theoretical implications of the evidence from comparison of marine and terrestrial macroecological patterns.

Effects of predator presence on nematocyst uptake in the nudibranch Flabellina verrucosa in the southern Gulf of MaineKinsey Frick.* Department of Zoology, University of New Hampshire, Durham, NH 03824, USA; e-mail kinseym@cisunix.unh.edu.Aeolid nudibranchs maintain functional stinging nematocysts for protection against predators such as fish and crabs. Nematocysts are sequestered from the nudibranch’s cnidarian prey, and selection for incorporation is largely a function of availability in the diet. However, nematocyst ratios vary within nudibranchs feeding on a given diet, indicating that other factors may be involved in determining nematocyst selection. I propose that predator presence influences nematocyst incorporation from those available in the diet, as nematocysts are a primary defense mechanism for combating predation. Nematocyst uptake in the nudibranch Flabellina verrucosa collected from the southern Gulf of Maine was examined in response to various predators, including Crossaster papposus, Tautogalubrus adspersus, and Carcinus maenas, and compared to uptake due to diet alone. F. verrucosa is a potential prey source for these predators, though not all are present in the collection area, thus nudibranch experience with these predators spanned the range of common exposure to no possible exposure to the experimental predator. Nudibranchs in individual flow-through containers feeding on a provided diet of the hydroids Tubularia crocea and Obelia spp. were subjected to tanks containing a predator, then the nematocyst distribution within the nudibranch cerata was examined. While the majority of the changes over the experimental period were attributable to diet as previously shown, nudibranchs responded to both the cunner T. adspersus and the sea star C. papposus stimulus by significantly increasing incorporation of microbasic mastigophores, a penetrating type of nematocyst. No differential uptake was seen with C. maenas; however, response was evident in the nudibranchs both for predators present in the collection area, and those with which they could have had no previous exposure. This indicates that in addition to diet, F. verrucosa, and possibly other aeolid nudibranchs, modulate nematocyst incorporation in response to the presence of predators in the area.

Factors determining the composition of infaunal beach communities at large scalesM. T. Frost,1 M. J. Attrill,1 A. A. Rowden,1,2 1Benthic Ecology Research Group, University of Plymouth, United Kingdom; 2present address: Marine Biodiversity Group, National Institute of Water & Atmospheric Research (NIWA), Wellington, New Zealand.There have been many studies examining the effects of small-scale factors such as grain size and exposure on sandy beach infaunal communities. There have been relatively few looking at large scale factors however, and in 1999 a study carried out on sandy beaches around the British Isles showed that tidal fronts which separate mixed and stratified water bodies may influence community variation between beaches at larger scales. To investigate large-scale processes on sandy shores, beaches were sampled in three biogeographic provinces (boreal, boreal-lusitanean and lusitanean boreal) and fronts selected within each of these provinces; the Orkney front around northeast Scotland and Orkney Islands, the Scilly front around southwest England and the Iroise front off Brittany in northwest France. Samples were taken in each of the provinces, within and outside frontal boundaries. Analysis has been undertaken using both univariate (ANOVA) and multivariate (PRIMER) techniques. The results show differences between beach infaunal community composition between the biogeographic provinces, as well as differences in univariate measures such as diversity. SIMPER analysis revealed the isopod Eurydice as being a major taxon contributing to dissimilarity. This genus occurs in all three provinces but with different species or species combinations being present in each. The differences between communities on beaches in mixed and stratified waters (i.e.within and outside tidal front boundaries) are less clear, but still indicate some degree of separation. These patterns are discussed and the relative contributions of the small-scale factors such as beach type, and the large-scale factors such as temperature and biogeographic province are assessed.

Caging—an ecologist’s friend or foe?Leslie J. Gallagher* and Kenneth L. Heck, Jr. Dauphin Island Sea Lab and University of South Alabama, Dauphin Island, AL 36528, USA.Despite their well-known potential to produce significant artefacts, caging experiments remain a staple item in the benthic ecologist’s toolbox. We used field studies to evaluate the significance of several potential artefacts associated with conducting caging experiments in low energy seagrass beds. This work demonstrated that cage structure significantly influenced velocity of water flow and sediment composition. Such alterations in physical properties were associated with a change in the number and community composition of new recruits settling inside cages. However, cage structure had little effect on overall densities and species composition of macrofauna (> 500 um), and inclusion/exclusion of predatory pinfish (>8 cm) had no significant effect on the immigration and emigration rates of potential prey species. These results suggests that short-term (~ 1 month) caging experiments in low energy seagrass habitats that focus on macrofauna can be an effective tool in understanding the ecology of these systems, and that careful planning can limit the impact of caging artefacts.

Seed dispersal and landscape-scale dispersal limitation in the cobble beach plant metacommunityJacqueline L. P. Gamiño,* Margaret A. Dolan, and John F. Bruno. The University of North Carolina at Chapel Hill, Department of Marine Sciences CB#3300, 12-2 Venable Hall, Chapel Hill, NC, 27599-3300, USA.Dispersal is a key process in marine communities and can have profound effects on population- and community-level parameters. Several new lines of inquiry within marine ecology are largely dependent on an ability to quantify dispersal characteristics. Since dispersal can have a large influence on population connectivity, the implications for population management and reserve design are obvious. Additionally, dispersal has been described as the key variable in metapopulation ecology. For example, the details of migration essentially dictate the effects that landscape attributes will have on large-scale species distributions and dynamics. Unfortunately, it is very difficult to obtain even basic dispersal data for most species. We quantified the dispersal-distance function of several plant species that inhabit the cobble beach plant metacommunity. We sampled seed supply as a function of distance from the parental source population over four years at a number of sites. We found a surprising degree of seed retention that is suggestive of very low rates of emigration and evidence of relatively long distance dispersal (≈500 m). When combined with data on the spatial arrangement of habitat patches and patterns of patch occupancy and colonization, our results indicate that patch isolation is a significant cause of dispersal limitation in this system. In this metacommunity, frequencies of patch occupancy are quite low (0.01 to 0.40) and many habitable patches remain unoccupied. Thus, dispersal limitation and patch isolation appear to significantly affect the dynamics of this metacommunity.

The distributional ecology of Johnson’s seagrass (Halophila johnsonii), in southeastern FloridaAdam Gelber,1* Donald R. Deis,2 and William F. Precht.1 1PBS&J, 2001 N.W. 107th Ave., Miami, FL 33172, USA; 2PBS&J, 7785 Baymeadows Way, Suite 202, Jacksonville, FL 32256, USA.Halophila johnsonii (Johnson's seagrass) was listed as a threatened species in 1998 making it the first marine plant species to be listed under the Endangered Species Act because it was considered susceptible to perturbations, limited in distribution, and lacking in the ability to disperse by sexual propagation. It has one of the most restricted geographical ranges known for any seagrass in the world and is one of the least abundant where it occurs. The range of the species includes inland and estuarine waters from Sebastian Inlet in the Indian River Lagoon to the middle of Biscayne Bay. Available distributional data revealed distinct gaps in available data on distribution, particularly in the southern end of the range in Biscayne Bay. Collecting additional distribution data and delineation of the southern end of the range became a focus of field surveys associated with this study. Additional distribution data was also added at the northern end of the range. A Geographic Information System database was created by the collection of all existing data sets containing locational information on the species along with the products of the current field surveys. This project has begun to fulfill some of the first tasks described in the recovery plan for the species.

Oxidative DNA damage in estuarine bivalvesM. L. Gielazyn,1* A. H. Ringwood,2 S. E. Stancyk,1 and W. W. Piegorsch.1 1University of South Carolina, Columbia, SC, USA; 2Marine Resources Research Institute, Charleston, SC, USA.Elevated levels of chromium are found in marine water and sediment near urban and industrial areas worldwide. Hexavalent chromium, Cr(VI), the predominant valence state in seawater, readily passes through cellular membranes. Once inside the cell Cr(VI) is reduced to trivalent chromium, Cr(III), by cellular reductants. Exposure to Cr(VI) can result in numerous forms of DNA damage. A portion of the DNA damage is thought to be oxidative, due to reactive oxygen intermediates and Cr species produced during Cr(VI) reduction. Single cell gel electrophoresis or the comet assay is a simple and sensitive technique used to examine DNA damage in single cells. Endogenous enzymes that repair DNA can be used in conjunction with the comet assay to identify different types of DNA damage. For example, the lesion-specific enzyme formamidopyrimidine glycosylase (FPG) recognizes 8-oxyguanine and other damaged bases, which are products of oxidative damage. Experimental objectives were to use the comet assay to quantify DNA damage (single strand breaks and alkali-labile sites) and oxidative DNA damage in bivalve tissues. Oyster (Crassostrea virginica) hemocytes were exposed to Cr(VI) (as K2Cr2O7) and H2O2 under controlled laboratory conditions. The comet assay was used with and without FPG to determine the amount of DNA damage in oyster tissues. We have found an increase in single strand DNA breaks and alkali-labile sites in hemocytes after exposure. FPG studies indicate that oxidative damage is contributing to observed DNA damage. DNA damage can lead to necrosis, apoptosis, or heritable mutations, and therefore has the potential to impact populations as well as individuals. Recent studies using a similar experimental design with clam (Mercenaria mercenaria) hemocytes suggest that clams are more sensitive than oysters.

Life at the edge: examination of the northern geographic range limit of an intertidal snailS. E. Gilman.* Center for Population Biology, University of California, Davis, CA 95616, USA.For many terrestrial species the poleward edges of ranges are determined by climate and physiological stress while the equatorward edge is determined by species interactions. There is significantly less evidence for this paradigm among marine species, and only a few studies have examined the range limits of any intertidal species from the Northeastern Pacific. For species with a planktonic larval stage, ocean currents could also determine the location of range limits. The intertidal limpet Macclintockia scabra is distributed from Mexico to Cape Mendocino, CA. I am studying the northern range limit of M. scabra to compare the relative influence of physiological stress and recruitment limitation on this range limit. Preliminary results from transplanting M. scabra north of Cape Mendocino do not show a consistent relationship between latitude and survival or growth rates. In contrast, a study of recruitment shows a decline in recruitment rates with latitude. I will discuss possible factors determining the northern range limit of M. scabra in light of this data.

Chemical ecology of reef and cave sponges of the Bahamas: predator deterrent vs. antimicrobial activityD. J. Gochfeld1* and M. Slattery.1,2 1National Center for Natural Products Research and 2Department of Pharmacognosy, University of Mississippi, University, MS 38677, USA.The sponge Plakortis sp. is common on reefs throughout the Caribbean; in the Bahamas it is found on shallow and deep fore-reefs, as well as in marine caves. We compared the chemical ecology of the sponge Plakortis sp. from both reef and cave habitats near Lee Stocking Island, Bahamas. These habitats differ considerably in both physical and biological parameters, including light, water motion, and microbial and predator communities. Reef sponges are potentially subject to high levels of predation, and both the sponges and their extracts were more deterrent to fish than were cave sponges. Whereas marine caves are free of predatory fishes, they do act as microbial sinks that concentrate a microbial community on the cave substratum, although the associated sponge fauna is relatively free of microbial overgrowth. By comparison, reef sponge surfaces harbor significantly more microbes than do their cave counterparts. Extracts of cave sponges exhibited greater antimicrobial activity against cultured marine microbes than did reef sponge extracts, and phytagel discs embedded with cave sponge extracts were significantly less susceptible to fouling than were those containing reef sponge extracts. There appears to be a tradeoff between predator deterrent and antimicrobial chemical defenses in the reef vs. cave habitats.

Grazing preferences of marine isopods, amphipods, and gastropods on three prominent algal species of the Baltic SeaM. E. Goecker1* and S. E. Kåll.2 1Dauphin Island Sea Lab/University of South Alabama, 101 Bienville Blvd., Dauphin Island, AL 36528, USA; 2Åbo Akademi University, Department of Biology/Environmental and Marine Biology, Åbo, Finland 20500.Preference tests were performed over a two-week period in September 2001 in which isopods (Idotea spp.), amphipods (Gammarus spp.), and gastropods (Theodoxus fluviatilis) were offered choices of three common algal species from the Baltic Sea: Enteromorpha intestinalis, Cladophora spp., and Fucus vesiculosus. After a 48-hour starvation period, 20 of each grazer species were placed in aquaria containing ~1.0 g of each algal species. Fifteen trials for each grazer were run for 20 hours. We found that Gammarus spp. ate significantly more Cladophora spp. and E. intestinalis than F. vesiculosus (p < 0.001). Similarly, Idotea spp. ate significantly more of both filamentous green algae than F. vesiculosus (p < 0.001). T. fluviatilis showed no preferences among algal species with almost no consumption. With the preference of isopods and amphipods for filamentous green algae, we would expect these algae to be maintained at low biomass levels, but this is not the case in the Baltic Sea. We suggest two factors that may be promoting accumulation of algal biomass. Clearly, bottom-up effects of high nutrient loading have caused high growth rates of filamentous algae, negating effects of preferential grazing. Second, removal of piscivorous fish may be producing a top-down effect on herbivore abundance, and thus herbivore ability to control filamentous algal biomass. More likely a combination of factors plays a role in grazer regulation of fast growing, filamentous algae. With further study on grazing rates, densities of animals, and growth rates of algae, more insight can be gained on grazer influence of algal overgrowth.

Assessing whether oyster reef habitat functions as fish foraging groundsJonathan H. Grabowski,* Adam J. Baukus, Kevin M. Sullivan, and Rachael Wagaman. University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC, USA.The decline of the oyster fishery in the eastern United States continues even though oyster reefs are beginning to receive recognition for the important ecosystem services they perform. In addition to production of oysters for harvest, oyster reefs stabilize other critical habitats, filter water, and create habitat for economically valuable finfish and mobile invertebrates. Oyster reefs typical harbor greater densities of prey fishes, crustaceans, polychaetes, and mollusks than surrounding unstructured bottom; however, biogenic structure created by oyster reef habitat may limit predator access to reef-associated prey. We conducted experiments in 1-m2 mesocosms located within a laboratory settling-tank to determine whether oyster reef habitat enhances fish foraging rates. We manipulated oyster cover and conducted a series of predator-prey experiments in which we subjected common estuarine predator fish to mesocosms with reef habitat vs. ones with mud bottom. Each experiment consisted of one predator species (gag Mycteroperca microlepis or flounder Paralichthys spp.) and one prey species (mummichog Fundulus heteroclitus and white shrimp Penaeus setiferus). Prey survivorship was quantified to estimate predator foraging rates. Gag consumed significantly more mummichog on reefs than on mud bottom, whereas reef habitat did not affect gag foraging rates on white shrimp. Conversely, flounder consumed more shrimp on mud bottom than on reef habitat. Flounder did not forage effectively on mummichogs in either habitat. Habitat structure can influence predator foraging efficiency; therefore, predator-prey interactions on oyster reefs are dependent on predator foraging behavior.

Ice age kelp forests: climate-driven changes in kelp forest distribution and productivity since the last glacial maximumMichael H. Graham.* Center for Population Biology, University of California, Davis, California, USA, 95616, USA; e-mail mhgraham@ucdavis.edu.Kelp forest distributions are constrained by the availability of rocky substrate within the depth range tolerable for growth and reproduction. The size and distribution of such reefs may vary over relatively short geological timescales (100’s of yrs) due to interactions between coastal bathymetry and climate-driven changes in eustatic sea level. I developed a digital bathymetric map for the southern California coast. Using a Geographic Information System (GIS) and published sea level curves and kelp depth tolerances for the same region, I reconstructed changes in the maximum size, distribution, and productivity of insular giant kelp (Macrocystis pyrifera) forests in the Southern California Bight since the last glacial maximum. Comparing the known size and distribution of present-day giant kelp forests to GIS predictions based on current sea level validated reconstructions. Reconstructions predicted that the total area of available kelp forest habitat was approximately 200% greater at 16.5 kyr BP (1130 square km), than at present (382 square km). Available kelp forest habitat during the last glacial maximum (18.5 kyr BP; 628 square km) was approximately 64% greater than at present, the difference between 16.5 and 18.5 kyr BP being due to greater exposure of the steep shelf slope during lowest sea levels. Coupled with area-specific biomass and productivity estimates from present-day kelp forests, these reconstructions suggested more productive and spatially extensive kelp forests in the Southern California Bight near the last glacial maximum than at present. The large climate-driven (i.e. sea level) decreases in kelp forest distribution and productivity since the last glacial maximum likely had important historical impacts on the ecology and evolution of the present-day kelp ecosystem, as well as the exploitation of marine resources by the early human inhabitants of southern California.

Mortality estimates of the southern bay scallop (Argopecten irradians concentricus), in the Gulf of MexicoJaime M. Greenawalt,* Thomas K. Frazer, and Stephanie R. Keller. University of Florida, Department of Fisheries and Aquatic Sciences, 7922 NW 71st St., Gainesville, FL 32653, USA.Historically, the southern bay scallop (Argopecten irradians concentricus) has been an important recreational fisheries species along the Gulf coast of Florida. However, a decline in scallop abundance resulted in regulation changes in 1995, including a closure to harvest south of the Suwannee River. Although the cause of the population decline is unknown, it is potentially a result of over fishing. Populations in some areas of the closed regions have since rebounded to "healthy" densities of 13 and 33 per 50m2, in 2000 and 2001 respectively. Quantitative estimates of fishing mortality and natural mortality are required to develop an effective management plan for the bay scallop fishery. This study provides the necessary estimates through a comparison of the mortality rate of a fished and unfished population. Two local populations of bay scallops (one subject to harvest and another in an area closed to harvest) were sampled by visual benthic surveys prior to the fishing season, and at monthly intervals until after the close of the fishing season for two years. Catch curves were used to estimate the total mortality for both populations, and subsequently to estimate fishing mortality and natural mortality rates for two years. The decrease in density thoughout the season in the area open to harvest (Steinhatchee) can be attributed to both fishing mortality and natural mortality. Whereas, the seasonal density declines in the closed region (Homosassa) represent only natural mortality. Simulations of increased exploitation were run to determine the effect that increased harvest pressure may have on the sustainability of bay scallop populations. Results from this study may play an important role as closed areas are reopened to harvest in 2002.

Characterization of the development of fish cage fouling communitiesJennifer Greene* and Raymond Grizzle. University of New Hampshire, Jackson Estuarine Laboratory, 85 Adams Point Road, Durham, NH 03824, USA; e-mail jenn.greene@unh.edu or ray.grizzle@unh.edu.A major problem with open ocean aquaculture of finfish in the Gulf of Maine is the growth of algal and invertebrate communities on the surface of the cages. These organisms add weight and drag to the cage, affecting its behavior under different wave and current conditions. In 2000, an estimated $40,000 was spent to routinely remove the organisms from the two cages. This project will characterize successional development of these communities to better understand the dynamics of the populations that inhabit this unique, floating habitat. A six-month preliminary experiment was started in December 2001 to provide data for the design of a year-long experiment commencing in June 2002. Three experimental net panels, each consisting of a 30x30 cm CPVC square frame with knotless nylon net stretched and cable-tied evenly over it, were attached to each cage. One cage is at a water depth of 15 m and the other is at the surface. Two of the panels will stay out for the entire six months. Two more panels will be deployed each month with one being collected monthly and the other staying out for the duration of the preliminary experiment. Hence, monthly recruits as well as successional sequences of different durations will be monitored. Retrieved panels were photographed, plastic-wrapped and stored on ice until returned to the lab for processing. The first month (December) panel from the surface cage showed an initial colonization by filamentous diatoms (Melosira, Biddulphia, and Licmophora), skeleton shrimp (Caprellidae),and mussels (Mytilidae). The first month panel from 15 m showed little to no algal colonization while skeleton shrimp and mussel spat dominated. During the second month (January), the surface panel showed similar abundant diatom growth but no invertebrates, while on the 15 m panel, skeleton shrimp remained abundant but mussel spat and diatoms were absent.

Is dissolution of gypsum stone a sufficient proxy for water flow in ecological studies?Kevan Gregalis,* Sean P. Powers, and Melissa Boykin. University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC 28557, USA.For field ecologists, determining mechanistic explanations for patterns in nature requires that differences in physical/chemical parameters be determined. When investigations move from small-scale, single-site manipulations to larger field studies, the need for cost-effective methods to estimate environmental differences becomes critical to the success of the study. However, the high-unit cost of unattended sampling instrumentation prevents the use of high-resolution sam-pling equipment at multiple sites. In many cases a time-integrated proxy of the parameter in question may be sufficient to evaluate differences within or among sites. In this vein, aquatic ecologists have relied on the dissolution of gypsum stone as a means of measuring spatial heterogeneity in water flow patterns; however, the efficacy of using the dissolution rate of gypsum molds as a proxy for water motion has been questioned. We present the results of a relatively simple set of field experiments designed to determine if the dissolution of gypsum molds corresponded to manipulated patterns of water motion. Water flow was manipulated in situ by use of large plywood channels. Water velocity was increased or decreased compared to ambient levels by varying the width of the opening relative to the width of the center, working section of the channels. Comparisons between velocity measurements collected within the channels using current meters and dissolution rates of gypsum molds demonstrated a high degree of correspondence (R2 > 0.75; p < 0.05). Additional experiments were performed to compare dissolution rates under similar current speeds, but dissimilar flow patterns. This was achieved by comparing gypsum dissolution in channeled flows to dissolution rates in areas where flow was unre-stricted. The results of both sets of experiments demonstrate the usefulness of dissolution of gypsum molds as proxy for differences in water flow.

Long-term changes in intertidal oyster reefs and the potential effects of boating activitiesRaymond Grizzle,1* Jamie Adams,1 and Linda Walters.2 1Jackson Estuarine Laboratory, University of New Hampshire, Durham, NH 03824, USA; ray.grizzle@unh.edu; 2Department of Biology, University of Central Florida, Orlando, FL 32816, USA.Previous research had shown that some intertidal oyster (Crassostrea virginica) reefs in the Mosquito Lagoon within the Canaveral National Seashore, Florida had dead margins consisting of mounded up, disarticulated shells. It was hypothesized that boating activities were the cause of the damage because all the reefs were adjacent to major boating channels. We characterized the history of the appearance of dead margins using aerial photographs taken between 1943 and 2000. Imagery analyzed included prints (black & white, color, or color infrared) from 1943, 1951, 1963, 1975, 1988, and 1995, and digital imagery from 2000 (USGS 1:12,000 digital ortho-quarterquads), at scales from 1:6,000 to 1:24,000. Prints were scanned at a resolution sufficient to yield 1-m pixels and referenced to the year 2000 imagery using ArcView and ArcInfo GIS software. All reefs with dead margins on the 2000 aerials were visited in November 2001 to confirm the presence and extent of dead areas. This provided a general ground-truthing for the "signature" (a highly reflective, light-colored area adjacent to darker-colored live reef) to be used to detect the appearance of dead margins in the historical aerials. The earliest appearance of dead margins was in 1975 on reefs adjacent to the Atlantic Intracoastal Waterway (ICW). The total number of reefs with dead margins and the total areal extent of dead margins increased over time. Our preliminary estimate is that about 15% of the total number of reefs in the Seashore have been damaged, with the most dramatic changes occurring in reefs along the ICW. This historical analysis provides strong (although only correlative) evidence that boating activity has detrimentally affected some reefs in the study area. Ongoing studies are aimed at further testing this hypothesis and elucidating the actual mechanisms involved.

Digestive symbionts of the fiddler crab Uca pugnax: who, where, and why?Lara K. Gulmann* and Lauren S. Mullineaux. Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.We are studying the gut microbiota of the fiddler crab Uca pugnax to determine the role of resident microbes in the digestive physiology of the host. U. pugnax consumes a diet of marsh detritus and benthic unicellular algae and could utilize microbial enzymes and/or fermentation products to maximize nutritional and energetic yield from its diet.Our first objective was to examine the gut lining for associated microbiota. Using scanning electron microscopy, we found that while the fore- and mid-gut sections were free from microbial attachment, the hindgut was densely colonized by bacteria and filamentous fungi. The majority of bacteria observed were curved rod-shaped bacteria (2 μm x 0.5 μm). The fungi appear to be of the class Trichomycetes and order Eccrinales and produce hyphae approximately 10 μm wide and 5-20 mm long. To determine the consistency of the association and resolve any seasonal changes, we have made monthly direct counts of the resident hindgut microbiota. We found that bacterial densities are significantly higher (p<0.05) in the summer months, averaging 2.7 x 106 bacteria per mm gut length, as compared with winter months, when densities average 5.0 x 105 per mm. We expect that this seasonal difference reflects a reduction in food consumption during the crabs’ winter dormancy and highlights the microbiota’s dependence on host food supply. These results offer support for our expectation that the gut microbiota has a mutualistic role, but do not discount the possibility of a commensal association.

Variability in gut passage time of individual penaeid shrimp, with applications for aquacultureScott Hagins1* and Robert Feller.1,2 1Marine Science Program, 2Department of Biological Sciences, University of South Carolina, USA.Most physiological processes in marine crustaceans operate at rates that are highly dependent on extrinsic factors such as temperature and salinity. A widely cultured species of penaeid shrimp, Litopenaeus vannamei, is known to grow faster in salt-water impoundments when supplemental feed (shrimp chow) is added. Knowing the rate at which this additional food is processed is important for determining how much and how often to provide the growth-stimulating material. Selected feeding regimes should also take into account whether addition of extra feed will have negative impacts on water quality. Poor water quality’s negative effects on shrimp growth can negate the purpose of adding feed. Having learned in earlier studies that gut passage time (GPT) of juvenile shrimp can be highly variable (minutes to hours), we questioned whether this was simply due to the variability between shrimp or whether a single shrimp exhibited such plasticity. We examined GPT in L. vannamei in laboratory aquaria (21-27 psu) at room temperature (20-22°C) using a soy-based feed containing 30% protein, 7.5% lipid, and 5.3% fiber. Four feeding trials were conducted with each of eight shrimp. The time from first ingestion to first defecation was, with one exception, virtually constant between trials. Compared to field trials for the same species where direct observation is impossible and indirect methods must be used, the laboratory GPTs were about 17.5 minutes longer. Such consistent bias allows one to make direct comparisons between field and laboratory measurements of GPT and lends credence to the hypothesis that variation is in the food itself. Shrimp culturists can thus utilize laboratory-derived data such as GPT to improve their operational efficiency.