Lightning Talks - Living Marine Resources

Few studies have quantified trophic relationships in seagrass environments at the regional scale, making it difficult to make comparisons of trophic structures across seagrass ecosystems. We conducted a large-scale study at six sites across the northern Gulf of Mexico (Lower Laguna Madre, TX; Redfish Bay, TX; Chandeleur Islands, LA. St. George Sound, FL; Cedar Key, FL; and Charlotte Harbor, FL) during August–September 2018 to examine how trophic relationships in turtlegrass-dominated ecosystems vary across ~1500 km and 15 degrees longitude. We measured bulk carbon (δ13C) and nitrogen (δ15N) stable isotopes for 21 representative nekton species (n = 602 individuals) and 20 potential basal autotrophic carbon sources (n = 331 samples) that were common across all sites. Divergence in isotopic space and pairwise niche overlap between species and sites was evaluated using Stable Isotope Bayesian Ellipses (SIBER) and Niche Region and Niche Overlap Metrics for Multidimensional Ecological Niches (nicheROVER) techniques. Preliminary results indicate that seagrasses are an important basal carbon source for nekton species throughout the region, that variability in seagrass δ15N is similar among sites (-2.4 to 6.6), and that seagrass δ13C values may be more enriched in the western (-13.1 to -3.2) than the eastern Gulf (-18.9 to -9.6). These data provide useful information on food web structure in turtlegrass ecosystems at a macroecological scale that is directly relevant to natural resource management of these productive systems.

Bottlenose dolphin (Tursiops truncatus) strandings have been documented in Alabama since 1978, with enhanced data collection since 1996. Members of the public report sick, injured, and deceased marine mammals to the state stranding network and are asked to submit descriptions and/or photographs to confirm the species, location, and other necessary details of the stranding. One of these details is the sex of the stranded dolphin, which is vital to define mortality demographics and better understand underlying causes of death or at-risk members of a population through time. Sex identification can be difficult because dolphins lack external genitalia and internal examination (necropsy) of deceased individuals is not always possible due to scavenging, decomposition or inability to successfully salvage remains. To determine the effectiveness of the two most common sex identification methods, gross examination of photographs and necropsy, we compared sex ratios of 460 T. truncatus stranded in Alabama from 1996 to 2018. Sixty-eight percent (%) (n=313) were necropsied, of which 42% (n=131) were female, 54% (n=168) were male, and 4% (n=14) were unknown sex. Of the 147 carcasses that were not necropsied, 23% (n=34) were female, 40% (n=59) were male, and sex could not be determined for 37% (n=54) of individuals. We found that males were more easily distinguished via photograph than females because male genitalia are often distended during decomposition. The proportion of unknown sexes was lower and the proportion of female identifications was higher when animals were examined by necropsy (χ2= 67.98, p< 0.001 and p=0.003, respectively). These findings highlight the importance of necropsy and internal examination for sex determination in stranded dolphins and underscore the value of stranding response for obtaining complete demographic information needed to support cause of death determination and subsequent conservation actions.

Organisms may adjust characteristics such as behavior or morphology to reduce predation risk, but in doing so suffer reductions in growth and fecundity. To balance conflicting needs of reducing risk with energy acquisition and growth, organisms often limit expression of predator avoidance or deterrence to situations where predation risk is high. Chemical cues are often used for risk evaluation and are known to cause changes in behavior and morphology for a variety of species. We investigated morphological changes in Eastern oysters (Crassostrea virginica) in response to chemical cues from two common predators, blue crabs (Callinectes sapidus) and oyster drills (Stramonita haemastoma). We evaluated changes in shell morphology including size and strength and also assessed how morphological changes affected oyster survival in laboratory feeding assays and when exposed to a natural suite of predators. After 6 weeks, oysters exposed to both predators had significantly stronger shells. In laboratory feeding assays as well as in the field, oysters grown with either blue crabs or oyster drills had significantly lower mortality (~20%). These findings indicated that oysters use phenotypic plasticity to reduce predation risk, suggesting that predator-induced changes in oysters may be a viable strategy for improving oyster reef restoration.

For more than 50 years, Sea Grant has established collaborative relationships across the United States, linking science to application. Recently, the Gulf of Mexico Sea Grant Science Outreach Team, the National Centers for Environmental Information (NCEI), and the Northern Gulf Institute (NGI) partnered to expand the use of long-term records of coastal and oceanographic data that support environmental prediction, scientific analyses, and formulation of public policy. NCEI is a leading authority for environmental information; their data stewardship maximizes NOAA’s investment in environmental research, converting scientific insights into dynamic, usable information that inform strategy and decision making in government, academia, and the private sector. The audience will learn about the Deep Sea Coral Data Portal created for NOAA Fisheries’ Deep Sea Coral Research and Technology Program (DSCRTP) by NCEI. This Portal provides access to deep sea coral and sponge data, images, and technical reports from research funded by DSCRTP and its partners. Users of the Portal’s digital map can search, discover, and download datasets from the National Deep-Sea Corals and Sponges Database. The map also features a custom search interface with filters for taxonomy, region, time frame, and depth range, and includes model overlays that project coral and sponge habitat suitability and population level projection for different locations and regions. Nearly 5 years after its initial launch, the Portal is set to undergo a rebuild. Members of NCEI, DSCRTP, and Sea Grant are seeking feedback on the utility, usability, and future needs for the Portal and its underlying databases.