Altizer, C.E. (GPMB, College of Charleston), Ballenger, J. (SCDNR), Martore, R. (SCDNR), Reichert, M. (SCDNR), and Sancho, G. (College of Charleston)
Artificial reefs are frequently used to enhance fish populations, provide new recreational fishing opportunities, and mitigate habitat loss. Habitat age heavily influences community structure in terrestrial habitats but has not been definitively tested for fish communities at artificial reefs. Previous studies tracking succession of fish communities on new artificial reefs have used short time scales (≤5 years) and focused primarily on tropical reefs, so little is known about community development on temperate systems. This study will present preliminary results from a historical data set monitoring ecological succession at an artificial reef system in South Carolina. SCUBA video surveys of fish communities were conducted from June 1999 to November 2002 at Area 51, an unpublished artificial reef system made of concrete cones and divided into four identical corners. Two corners experienced controlled fishing pressure for the duration of the study. Additional video data were collected in July 2012, ten years after fishing pressure ceased. The results show how species richness, evenness, diversity, fish density, and community structure change over time and how fishing pressure affects these parameters. Furthermore, these results may help advise fishing and conservation regulations based on when economically important species start to dominate artificial reef fish communities.
Anderson, A.P. (GPMB, College of Charleston), Darden, T.L. (SCDNR), and Denson, M.R. (SCDNR)
In order to properly manage a species over a large geographic area, it is necessary to understand the genetic relationship both among and within river systems in order to identify appropriate management units. Determining changes in this relationship is also important in understanding how stocking may have and continues to influence these genetic relationships. We used a suite of 12 microsatellites developed for striped bass to evaluate patterns of gene flow both spatially and temporally across the Carolinas. Our results suggest striped bass in the Santee-Cooper river system have been and remain a single population. Additionally, the historical samples suggest that the population was undergoing inbreeding; however, the contemporary samples suggest that inbreeding is no longer occurring. Striped bass in the Roanoke and Cape Fear represent a single population most likely due to historical transfer stocking across the State from Roanoke River stock. Watersheds in South Carolina are genetically distinct from each other and North Carolina, although the genetic difference between the ACE Basin and Santee-Cooper System has dramatically decreased over fifteen years likely due to a large number of Santee-Cooper hatchery-produced fish being stocked into the ACE Basin. With a clearer picture of striped bass population dynamics across the Carolinas, managers can improve their efforts in genetic management and restoration of striped bass populations.
Anweiler, K. (GPMB, College of Charleston) and Denson, M. (SC Department of Natural Resources)
Spotted seatrout are vulnerable to winter mortality when air temperature drops, causing shallow water to chill rapidly. Temporary closures in response to population declines should be based on a thorough understanding of the magnitude of winter mortality. In this study, we used the chronic lethal method (CLM) to determine temperatures that are lethal to spotted seatrout when exposed to a -1° C/day change in temperature. Spotted seatrout (n=24) were found to experience loss of equilibrium at a mean (± SD) temperature of 3.57° ± 0.24° C, and mortality at a mean temperature of 3.08° ± 0.31° C. In the next phase of the study we are evaluating how spotted seatrout are affected by prolonged, sub-lethal temperatures, and how seatrout mortality is affected by temporary cooling and warming periods. These experiments use a modified acclimated chronic exposure (ACE) method, which allows acclimation to changing temperatures (-1° C/day) until a pre-determined base temperature is reached. The ACE method is performed with both static and fluctuating temperatures, at two base temperatures (5.25° and 4.25° C). These experimental temperature regimes mimic the natural variability observed in the environment. Fish (n=23) exposed to a stable temperature of 5.25° C for 5 days displayed 0% mortality, while fish (n=23) exposed to temperatures that fluctuated between 6.5° and 4.0° C displayed 4% mortality. The results of this study will be used to develop predictive management tools that incorporate these environmental parameters.
D'Aguillo, M.C. (GPMB, College of Charleston), Harold, A.S. (College of Charleston), Roumillat, W.A. (SCDNR), Darden, T.L. (SCDNR), and Wyanski, D.M. (SCDNR)
Ontogenetic shifts in diet allow organisms to maximize energy conservation, presumably by reducing the time spent foraging or increasing net energy intake. As many diet studies are descriptive and report only frequency or counts of prey items, the ability to precisely quantify and describe a diet shift can be challenging. The goals of this study were to report the diet composition of the Naked Goby, Gobiosoma bosc, and examine if there is a threshold body size at which the diet shifts from dominance of meiofauna to dominance of macrofauna. Gobiosoma bosc specimens were collected from oyster reefs in the Charleston Harbor estuary by examination of removable oyster shell and seine. To investigate diet composition, the digestive tract was removed from G. bosc individuals and prey types were identified to the lowest taxonomic level possible, measured, and enumerated. Stomach content analysis reveals G. bosc primarily consumes harpacticoid copepods from the meiofauna, and polychaetes and amphipods from the macrofauna. The consumption of macrofauna begins at a small predator size (11 mm standard length), and while the number of macrofaunal organisms ingested does not increase with predator size, the volume of macrofauna does. Both the number and volume of meiofaunal organisms consumed decreases with predator standard length, suggesting strong reduction of meiofauna in the diet around a predator size of 25 mm. The use of different prey response variables to characterize a diet shift, with insights into the potential roles of morphology and behavior driving this particular diet shift, will be discussed.
Fisher, L. (GPMB, College of Charleston)
Incubation temperature has significant developmental effects on oviparous animals, including determining sex for several species. For the Northwest Atlantic loggerhead sea turtle (Caretta caretta), apparent population-wide female-biased hatchling sex ratios contrast with observations of juvenile populations, where sex ratios have remained constant at about 2 to 1 female-biased over the past 30 years. It has been suggested that some unknown factor is affecting loggerhead survival resulting in an unexplained differential loss of ~60% of female hatchlings per year. One theory to explain this hatchling mortality is tested in this project, that incubation temperature affects traits that influence survival. Furthermore, there may be differential survival between male and female hatchlings. I conducted laboratory experiments to test for an effect of incubation temperature on performance of loggerhead hatchlings. I tested 68 hatchlings produced from eggs incubated at 8 different constant temperatures ranging from ~27ºC to ~32.5ºC. Following their emergence from the eggs, I tested righting response, crawling speed, and conducted a 24-hour long hatchling swim test. Data indicate an effect of incubation temperature on survivorship, righting response time, crawling speed, change in crawl speed, and overall swim activity. Differences in performance of hatchlings incubated at high temperatures are important in light of projected higher sand temperatures due to climate change, and could indicate increased mortality from incubation temperature effects.
EFFECTS OF HYPOXIA ND LOW pH ON MOSQUITO INSECTICIDE TOXICITY IN TWO COMMERCIAL SHELLFISH SPECIES
Garcia, R. (GPMB, College of Charleston), DeLorenzo, M. (NOAA/NOS/CCEHBR), Chung, K. (NOAA/NOS/CCEHBR), Key, P. (NOAA/NOS/CCEHBR), Burnett, L. (College of Charleston, and Coen, L. (Florida Atlantic University)
Insecticides are commonly used to control disease-carrying mosquitoes in coastal areas. This study aims to assess the risks of mosquito control insecticides to commercial molluscan species under various abiotic conditions. The effects of mosquito control insecticides on molluscan survival were determined at 96 h (larval and juvenile life stages) and 21 d (juvenile life stage) in the eastern oyster, Crassostrea virginica, and the hard clam, Mercenaria mercenaria, using two pyrethroids, resmethrin and permethrin, and the organophosphate, naled. Larval clams were more sensitive to resmethrin and permethrin than oysters. Naled was the most toxic compound tested in oysters. Larval clams were more sensitive to resmethrin than juvenile clams. Larval oysters and juvenile oysters were similar in sensitivity to the insecticides tested. Toxicity increased with chronic exposure except for resmethrin in juvenile clams. Effects of insecticides on growth (dry weight, shell area) were determined after 21 d in juvenile clams and oysters. Permethrin and naled caused decreased growth in juvenile clams, while all three compounds caused decreased growth in oysters. To determine whether stress from abiotic factors would modify insecticide toxicity, a larval clam acute test was conducted; comparing normal oxygen conditions and hypoxic (low dissolved oxygen) conditions with and without resmethrin exposure. There was a significant effect of hypoxia on resmethrin toxicity, with an eight-fold increase in toxicity (percent of control survival) under hypoxic conditions. Currently, we are testing the effects of low pH and a combination of hypoxia and low pH on resmethrin toxicity.
Kendrick, B. Jacob (GPMB)
Emiliania huxleyi (Ehux) is a cosmopolitan coccolithophorid which forms very dense blooms annually that impact the global cycles of carbon and sulfur. These blooms are known to be terminated by host-specific viral infection making this host-virus system extremely important to understanding how the biosphere affects the atmosphere and how oceanic ecosystems may respond to further climate change. Recently, it was found that Ehux strain CCMP 374 is resistant to viral infection if incubated at 21°C but susceptible to infection at 18°C. Being able to easily induce resistance has allowed an unprecedented look into possible mechanisms for active viral resistance as seen in certain E. huxleyi strains including changes in host intact polar lipids. Results will be presented outlining fundamental changes in the host physiology, including the lipidome, in response to increased temperature and successful viral infection. These results also confirm previous research into the mechanisms by which successful infection occurs.
Meadors, W. (GPMB, College of Charleston) and Arnott, S. (SCDNR)
Fish skin lesions may be caused by a variety of factors including disease, toxic plankton blooms or water contaminants, and they are sometimes indicative of poor environmental conditions. Lesions can have negative impacts on affected individuals and may also affect the health of fishermen who come into contact with them. Anecdotal evidence suggests that skin lesions are especially common and severe on red drum, Sciaenops ocellatus, during the winter months in Winyah Bay, South Carolina. The primary objective of this study was to complete a systematic, year-round study of thirteen SC estuaries to quantify the spatial and temporal distributions of red drum lesion prevalence and severity. I hypothesized that lesions were more common and more severe in Winyah Bay during the winter, and further tested whether fish size affected lesion occurrence. Fish were collected from August 2011 – September 2012. All red drum were measured and assigned a lesion severity score before being released. Over the study period, a total of 3886 red drum were examined, of which 175 had lesions. 48% of the affected red drum were captured in Winyah bay. Additional blood studies are being performed on lesioned versus non-lesioned fish to assess a variety of potential health indices.
Murray, D.C. (GPMB, College of Charleston), Reichert, M. (SCDNR), and Darden, T.L. (SCNDR)
Red porgy, Pagrus pagrus, is a protogynous hermaphrodite reef fish that associates with hard-bottom habitats in temperate waters. Red porgy has been a recreational and commercially important species over the past 30 years, and is managed as a single species under the SAFMC S/G complex. During the early 1980’s, increased fishing pressure began to significantly reduce the population in the South Atlantic Bight (Cape Hatteras, NC to Cape Canaveral, FL) resulting in a moratorium being enacted in 1999 due to a combination of low population size and high fishing mortality. The aim of this study was to determine how fishing pressure over the past 30 years has affected the genetic diversity of the population in the South Atlantic Bight. Nuclear DNA was extracted from historical samples, otoliths and fin clips, and genotyped using 9 microsatellite loci. An initial spatial evaluation of genetic diversity within the South Atlantic Bight was used to verify the previously identified lack of genetic structure using more robust sampling and marker designs. Genetic data coupled with life history data will allow for a temporal comparison of allelic diversity, heterozygosity, and effective population size. The results of this study should provide fisheries managers with critical information to allow for better preservation of genetic diversity of populations undergoing overfishing, as well as realistic considerations for rebuilding a population that is overfished.
Newby, J. (GPMB, College of Charleston) and Shedlock, A. M. (College of Charleston)
The spotted eagle ray, Aetobatus narinari,is a cosmopolitan myliobatoid recognized as near-threatened by the World Conservation Union however it is not protected in U.S. federal waters. A decreasing population trend, K-selected life history and primarily inshore, coastal habitat renders this species susceptible to over-exploitation by targeted fisheries, drift netting, and capture as bycatch. Since 2009 large seasonal aggregations have been observed in the Gulf waters of Sarasota, FL. Modest ecological data is available for A. narinari but almost no studies of fine-scale genetic structure exist. We are presently investigating the molecular ecology of this A. narinari population using fin clips from individuals (n=117) sampled non-invasively through Mote Marine Laboratory, Sarasota, FL, from April through December 2011 and genotyping across 8 microsatellite loci. Standard tests for Hardy-Weinberg Equilibrium, null alleles, linkage disequilibrium, and gene diversity (0.616) were performed. Analyses of statistically significant patterns of geographic structure on a latitudinal gradient (Structure and Arlequin, p=0.855) supported a single population opposed to several admixed populations. No evidence for sex-biased dispersal was uncovered using Structure and comparison of FIS values between genders (p=0.2057). Effective population size was estimated between 2,200 and 3,000 (LDNe and ONESAMP, respectively) indicative of large numbers of reproductively contributing individuals. Genetic results will be discussed in relation to A. narinari life history and management goals for this ecologically important elasmobranch.
O’Donnell, T. (GPMB, College of Charleston), Darden, T.L. (SCDNR), and Denson, M.R. (SCDNR)
Spotted seatrout, a recreationally important fish in SC, has recently suffered substantial population declines during the cold winters of 2000, 2009, and 2010 when water temperatures dropped substantially below long term averages. These winter-kills appear to result in population bottlenecks and their repetitive occurrence over a short time scale has prompted the SCDNR to consider a stock enhancement program. Prior to implementation of any management tactics, a full understanding of the population structure is required. The first goal of my thesis research is to determine the genetic population structure across eight estuaries along the southeast U.S. spanning NC to GA using a suite of 13 microsatellite markers. Results suggest significant population differentiation between fish in NC compared to SC and GA. Although we see a significant break in gene flow between these areas, the overall pattern throughout the sampling range represents a gradient in genetic diversification with the degree of geographic separation. A lack of appropriate habitat between SC and NC is likely driving the differences as some gene flow is still occurring across the barrier. The use of a powerful suite of markers has allowed higher structure detection than previous projects, which will improve future management of spotted seatrout in SC.
Shaw, A. (GPMB, College of Charleston), Frazier, B. (SCDNR), Sancho, G. (College of Charleston)
Estuaries serve as habitats and nurseries for many recreationally and commercially important fishes. Understanding the trophic ecology of the fish populations within estuarine communities is essential to effectively manage these species under an ecosystem-based management scheme. Upper-level predatory fish are among the most sought-after fisheries species by commercial and recreational fishers in this highly productive ecosystem. Determining the trophic ecology and dietary niches of predatory species is important to infer interspecific competition, relationships among the estuarine fish community and niche partitioning. Dietary niche overlap of the predator community in the Cape Romain National Wildlife Refuge (specifically Bulls Bay and its surrounding tidal creeks) was assessed using stable isotope analysis of muscle tissues of predatory species. Fishes of up to 10 species were collected via trammel nets, gillnets and longlines in the channels and along the banks of the estuary in cooperation of SCDNR. Tissue samples (approximately 60 mg) were taken from the dorsal musculature with a 4 mm biopsy punch and frozen until analysis. Comparison of C and N stable isotopes allows the inference of potential prey items, trophic level, and trophic niches of the analyzed species. Preliminary results suggest resource partitioning for finetooth sharks and red drum in addition to dietary overlap between the teleost predators, Atlantic sharpnose sharks and bonnethead sharks.
Smith, J. (GPMB, College of Charleston), Lee, P. (College of Charleston), Ditullio, J. (College of Charleston), Byrum, C. (College of Charleston) Janech, M.G. (College of Charleston, Department of Medicine, MUSC)
Ice-binding proteins (IBPs) belong to a multigene family and have been found in all polar ice-diatoms examined to date. IBPs serve to enhance survival of diatoms in frozen habitats. Environmental factors that influence the IBP expression include low temperature, and to a lesser degree, high salinity. Because sea-ice impedes the transmission of light we hypothesized that low light might also serve as a cue to elevate IBP expression. Ten different IBP RNAs were quantified at four time points using quantitative PCR. Three IBP RNAs were elevated up to 2.63-fold in low light compared to control at the final time point (p<0.05, two-way ANOVA w/interaction). Conversely, two different IBP RNAs were depressed 2.03-fold (p<0.001; two-way ANOVA w/interaction). When controlling for light, there were also significant changes within each group over time. In low light conditions, three IBPs indicated up to a 1.89-fold increase in IBP abundance (p<0.05; ANOVA). However, two additional IBPs when evaluated within equivalent light conditions underwent up to a 1.59-fold decrease (p<0.01; ANOVA). Among the control samples two IBPs showed up to a 2.17 fold decrease (p<0.05; ANOVA) and three others underwent up to a 1.43-fold increase over time (p<0.001; ANOVA). Under our laboratory conditions, a reduction in light level did result in the elevation of several IBP RNAs. However, these changes were modest, and for several IBPs, results contradicted our original hypothesis. Future studies will investigate whether low light is more likely to influence the expression of IBPs at lower temperature.
Smoot, S. (GPMB, College of Charleston), Couch, C. (Cornell University), Groner, M. (Atlantic Veterinary College), Kim C. (Cornell University), Siegmund, G.F. (University of Chicago), Singhal, S. (University of Washington), Harvell, C.D. (Cornell University), Wyllie-Echeverria, S. (University of Washington)
Many marine pathogens are opportunistic and can cause disease in only a subset of infected individuals. Relatively little is known about factors that influence pathogenicity or patterns of infection and disease across demographic or environmental gradients. We examined the etiology of the opportunistic protist pathogen Labyrinthula zosterae and patterns of wasting disease in its host, the eelgrass Zostera marina. We confirmed three of Koch’s postulates concerning the causative relationship between pathogen and host using field-collected Labyrinthula isolates from three sites in Washington, USA, and found that these strains varied in virulence. In a field survey, we quantified relationships between host size, disease prevalence and severity, and grazer (Lacuna sp.) abundance in eelgrass beds that are in decline. Disease prevalence and severity increased with shoot size at all sites, suggesting that more mature beds may be especially susceptible to disease. We present the first quantitative assessment of wasting disease in northeastern Pacific eelgrass and new methods for examining the host-pathogen relationship in the lab and field.
Tommerdahl, A. (GPMB, College of Charleston), Burnett, L. (College of Charleston), and Burnett, K. (College of Charleston)
As the size, intensity, and frequency of hypoxic zones continues to increase in nearshore marine habitats worldwide, it is important to understand the potential effects this will have on marine organisms. The penaeid white shrimp Litopenaeus setiferus and brown shrimp Farfantepenaeus aztecus are both found in high abundances in Charleston Harbor and provide good model organisms to study these effects; they inhabit estuaries that regularly experience hypoxia and play important ecological and economical roles. The related species Litopenaeus vannamei (Pacific whiteleg shrimp) is the most common aquacultured shrimp species worldwide, giving economic importance to understanding their ability to cope with hypoxia commonly found in aquaculture ponds. Previous studies have shown that hemocyanin (Hc), the respiratory pigment in these species, increases in concentration and oxygen affinity following chronic moderate hypoxia exposure. Our goals are to determine differences in Hc concentration and O2 affinity among the three species and characterize the effects of chronic hypoxia (30% air saturation) on these parameters. L. vannamei [Hc](10.0±0.27SEM g/100mL, n=35) is much higher than that found in both wild brown (4.7±0.53SEM g/100mL, n=7) and white (8.4±0.45SEM g/100mL, n=20) shrimp, with significant increases in [Hc] occurring in both wild species after at least 25 days in hypoxia. No discernible change in oxygen affinity was detected over this time. In contrast, selection for high growth and disease resistance in the aquaculture shrimp has presumably contributed to high basal [Hc] and O2 affinity that do not appear to respond to chronic hypoxia exposure. (NSF IOS-1147008).
Wickes, L. (GPMB, College of Charleston) and Etnoyer, P. (NOAA Center for Coastal Environmental Health and Biomolecular Research)
In the California Current System of the Northeast Pacific, water that is undersaturated with respect to aragonite is upwelled along the continental shelf, reaching the surface at some locations. Similar conditions are not predicted for open-ocean North Pacific waters for several decades. The Southern California Bight (SCB) thus provides a “natural laboratory” for studies of deep-water scleractinian corals growing under acidified conditions. The distribution of Lophelia pertusa in the SCB was characterized using photo and video surveys from >300 submersible dives from NOAA’s National Marine Fisheries Service. The environmental conditions surrounding Lophelia sites were assessed using data from the California Cooperative Oceanic Fisheries Investigations (CalCOFI) and an algorithm developed to estimate aragonite saturation (ΩA) from temperature and dissolved oxygen. Preliminary results suggest that coral in this region is found at the lowest aragonite saturation states ever reported for framework-forming scleractinians. Furthermore, dissolved oxygen averaged over the past four years is less than half the global average for the coral. Despite large variation in many environmental conditions for shallow sites relative to deeper sites in the Bight, perhaps a stressor in itself, the range of temperatures for Lophelia was remarkably narrow and closely matched global averages. At these depths and locations, Lophelia in the Bight is facing impending acidification, oxygen declines, and warming temperatures. The coral does not appear to form large reefs in the Bight and while identifying the environmental parameters that may limit growth, we hope to provide insight to the vulnerability of deep corals to ocean acidification worldwide.
Near, Thomas (Yale University)
Notothenioid fishes are an adaptive radiation in the near-shore marine habitats of Antarctica. This talk will profile the evolutionary history of this lineage of teleost fishes, relating patterns of diversification with periods of Antarctic climate change.
Near, Thomas (Yale University)
Charles Darwin: Natural history, a voyage of discovery, and a scientific revolution. Evolution is the only set of theory based on observed scientific facts that provides an explanation for the origin of maintenance of biodiversity on Earth. This talk will cover the life of Charles Darwin, discussing his discoveries in relation to evolution as a fact, and as a guiding focus for biological research in the 21st Century.