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Evaluation of modified Sphyrion tags for marking Caribbean spiny lobsters, Panulirus argus
Meaghan 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
estimates 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 (7690 mm CL) and large juveniles (61-75 mm CL), were used in the experiment. The lobsters were checked daily for
evidence of mortality 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 observed 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 treatments and grew less than their untagged female conspecifics. This study was conducted
during mating season for lobsters, 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 juvenile and adult lobsters.
The results of monitoring hard corals restored following the installation of telecommunication cables off
Hollywood, Florida
Donald R. Deis.* 7785 Baymeadows Way, Suite 202, Jacksonville, FL 32256; telelphone (904) 367-8683; facsimile
(904) 733-6621; e-mail [email protected].
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 comparison
A. 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 habitats
Theodore 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 oysterdominated 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, Antarctica
Jennifer 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 multidimensional scaling plot revealed a subtle gradation in community composition between different stages in recolonization 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 Ridge
M. B. Doerries* and C. L. Van Dover. Department of Biology, College of William and Mary, Williamsburg, VA
23187, USA; e-mail [email protected].
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 MidAtlantic 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 cinctipes
Megan 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 Keys
Scott 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 space
Meredith 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
gracilis
Joanne 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
landscape
C. 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 threedimensional 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 fluorescence
Mark 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 [I k], 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 (I k), 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 landscapes
Steve 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 191046018, 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 sitespecific. 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 connection
J. 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 multilevel 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 method
A. 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 metamorphosis
Angela 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, USA
Heat 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
[email protected].
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 corals
Peter 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 crab
David 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-theyear, 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 environment
G. 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 subtidal
Julie 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
are
produced, 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 reference
plots. 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 contents
Amy 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 sequences
Patrick 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 Maine
Kristine 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 results
Charles 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
experiment
Meredith 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 papillatus
Janna Fierst,* Janet Kübler, and Steve Dudgeon. California State University, Northridge
Northridge, 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 communities
Christopher Finelli.* Louisiana Universities Marine Consortium; 8124 Highway 56, Chauvin, LA 70344, USA; email [email protected].
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 Sanctuary
Geremea 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 ridge
Chuck 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 [email protected].
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 cool
Tara 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 halfyear post-settlement
Nicole 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 postsettlement, 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 UK
Andy Foggo.* Department of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK;
e-mail [email protected].
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 Maine
Kinsey Frick.* Department of Zoology, University of New Hampshire, Durham, NH 03824, USA; e-mail
[email protected].
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 scales
M. 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 largescale 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 metacommunity
Jacqueline 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 communitylevel 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 Florida
Adam Gelber,1* Donald R. Deis,2 and William F. Precht.1 1PBS&J, 2001 N.W. 107th Ave., Miami, FL 33172, USA;
2
PBS&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 bivalves
M. 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 8oxyguanine 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 snail
S. 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 activity
D. 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 Sea
M. 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 grounds
Jonathan 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
maximum
Michael H. Graham.* Center for Population Biology, University of California, Davis, California, USA, 95616,
USA; e-mail [email protected].
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 presentday 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 Mexico
Jaime 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 communities
Jennifer Greene* and Raymond Grizzle. University of New Hampshire, Jackson Estuarine Laboratory, 85 Adams
Point Road, Durham, NH 03824, USA; e-mail [email protected] or [email protected].
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 highresolution sampling 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 unrestricted. 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 activities
Raymond Grizzle,1* Jamie Adams,1 and Linda Walters.2 1Jackson Estuarine Laboratory, University of New
Hampshire, Durham, NH 03824, USA; [email protected]; 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 groundtruthing 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 10 6 bacteria per mm gut length, as
compared with winter months, when densities average 5.0 x 10 5 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 aquaculture
Scott 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 growthstimulating 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 laboratoryderived data such as GPT to improve their operational efficiency.