Department of Marine Science and Oceanography

Octopus predation and species selection contribute to community structure in benthic habitats, where plastic pollution accumulates. This study investigated how the bioactive plastic additive oleamide alters trophic interactions and behaviors of the common octopus (Octopus vulgaris) and its prey. We quantified activity budgets and trophic interactions for octopuses and multiple prey types (hermit crabs, free-living crabs, bivalves, and gastropods) before and after exposure to oleamide. Our analysis suggested that some taxa (octopuses and hermit crabs) exhibit more active behaviors during oleamide exposure. Free living crabs responded primarily to the threat of octopus predation, while other taxa did not show clear behavioral responses. Exposure to oleamide increased trophic interactions and the probability of mobile prey taxa being observed on the same side of the aquarium as the octopus, thus increasing the opportunity for predation. Our results support previous research showing that plastic leachates can impair decision-making, making prey more susceptible to predation.

Climate change has intensified thermal anomalies in coral reef ecosystems, contributing to coral bleaching and decline. As corals die, reef fragmentation increases, and species interactions in the benthos change. However, it is unclear which competitive interactions may prevail and structure future reef ecosystems. The aim of this thesis was to evaluate the effect of thermal anomalies on coral reef benthic competitive interactions. Photoquadrats in southeast Florida reef sites were assessed over 15-years to generate interaction metrics and determine effects on hard coral survivorship. A state-transition model was created to predict the resultant community across 100 years with thermal scenarios concordant with the IPCC RCP 4.5 and 8.5. Interaction doubled across three thermal anomaly events and ended up mainly composed of pairwise examples between Dictyota, Halimeda, Niphates erecta, and Erythropodium caribaeorum. Century projections confirm that soft coral and sponge interactions will increase through thermal anomalies. The survival of hard corals was more successful when colonies were in permanent or intermittent interactions than when colonies were solitary (indirect interactions). Living hard corals were mostly found interacting with the macroalgae, Dictyota, and sponge Aplysina cauliformis, while corals that died were mainly in interactions with the soft coral E. caribaeorum, and sponges N. erecta, C. delitrix, D. anchorata, and Ircinia campana. Future reefs will be composed of more interactions between soft corals and sponges as thermal anomalies intensify, which will result in a patchier and flatter community.

Sponges (Phylum Porifera) are hardy organisms persisting and predicted to become more dominant world-wide under climate change scenarios. However, we lack baseline knowledge on sponge biodiversity in transitional areas (subtropical to warm-temperate) that are more susceptible to climate change such as The Indian River Lagoon (IRL) (estuary) and Saint Lucie Reef (northern most coral reef) ecosystems in south Florida. The aims of this master’s thesis are to 1) evaluate if sponge assemblages reflect the previously defined ecotone between subtropical and warm-temperate biomes in the IRL (Chapter one), 2) determine how porifera communities are associated to their respective environment (temperature, water velocity, photosynthetically active radiation, carbonate chemistry, and nutrients) in the IRL and St. Lucie Reef (Chapter two), and 3) establish a distribution baseline for future studies aiming to assess Porifera range shifts during climate change (Chapter one and two). Porifera biodiversity surveys across the IRL and Saint Lucie reef were carried out at different spatial and time scales. Environmental parameters (ocean acidification, temperature and eutrophication) were obtained and compared for sites in Fort Pierce Inlet and St Lucie Reef. Chapter one results show that sponge assemblages do not reflect the previously defined ecotone between subtropical and warm-temperate biomes in the IRL, instead they structure in relation to the inlets (distance from the inlet). The most diverse sponge assemblages are found in Sebastian, Fort Pierce, and Jupiter Inlets, and are significant different among habitats; oyster reefs host a unique assemblage of excavating sponges.

Florida’s coral reefs are facing a multi-year coral disease outbreak described as stony coral tissue loss disease (SCTLD), affecting at least 24 species of scleractinian corals. Potential anthropogenic and environmental drivers of SCTLD progression and severity are still poorly understood. This project was designed to determine the potential impacts of elevated nutrients on the progression and spread of SCTLD on reefs in Southeast Florida. We attempted to increase nutrient levels near coral colonies using fertilizer amendments to mimic the effects of agricultural and urban runoff. SCTLD lesion progression, coral tissue loss, and disease prevalence were tracked overtime. There were no significant differences in nutrient concentrations between nutrient-amended and control groups or SCTLD progressions or surrounding SCTLD prevalence. However, water temperature was positively correlated to SCTLD activity. These findings provide insight to reef managers seeking to limit and mitigate the prevalence and impacts of SCTLD.

Marine sponges are one of the most prolific sources of chemical compounds with pharmaceutical importance. To establish a supply of such compounds large enough for clinical development, in vitro production methodology was investigated. Since all sponge cells do not divide in culture, it was hypothesized that the fusion of rapidly dividing cells of a sponge that does not produce any compounds of interest with cells of a nondividing but compound-producing sponge would result in a hybridoma that produces the compound of interest. In this study, hybridomas have been produced with cells of two marine sponges, Axinella corrugata, which produces the antitumor compound stevensine, and Geodia neptuni, which divides rapidly in a nutrient medium optimized for sponge cell culture. Successful hybridization and subsequent cell division and in vitro stevensine production may unlock the potential for sustainable mass production of other sponge-derived compounds.

Pond aquaculture accounts 65% of global finfish production. A major factor limiting pond aquaculture productivity is fluctuating oxygen levels, which are heavily influenced by atmospheric conditions and primary productivity. Being able to predict DO concentrations by measuring environmental parameters would be beneficial to improving the industry’s efficiencies. The data collected included pond DO, water temperature, air temperature, atmospheric pressure, wind speed/direction, solar irradiance, rainfall, pond Chl-a concentrations as well as water color images. Pearson’s correlations and stepwise regressions were used to determine the variables’ connection to DO and their potential usefulness for a prediction model. It was determined that sunlight levels play a crucial role in DO fluctuations and crashes because of its influence on pond heating, primary productivity, and pond stratification. It was also found that image data did have correlations to certain weather variables and helped improve prediction strength.

Bonefish Albula vulpes are an economically important sport fish that has historically bolstered the recreational flats fisheries of the Florida Keys and The Bahamas; an industry with an annual economic impact of US$465 million and US$169 million, respectively. Analyses of fishing guide logbooks and guide interviews indicate that the population of bonefish in south Florida has declined. Due to the economic and cultural importance of these fisheries, protection of spawning and nursery habitats is integral to population recovery and stability. However, knowledge gaps persist in how abiotic and biotic habitat factors influence reproduction and recruitment. Without clear delineation of spawning and recruitment habitats, bonefish populations remain vulnerable to anthropogenic disturbances. Bonefish partake in a unique three-point spawning migration, migrating from shallow-water home flats to form nearshore pre-spawning aggregations (PSA) before moving offshore to spawn. Using active acoustic telemetry, sonar imagery, and CTD profiles, the first complete account of offshore spawning movements and novel deep diving behavior was accomplished. Bonefish reached depths of 137.9 m and spawned at 67.3 m, a depth associated with the pycnocline/thermocline. Previous efforts show spatiotemporal plasticity in spawning, a behavior counter to other aggregation forming fishes.

Florida Pompano Trachinotus carolinus are molluscivorous, greater than 70% of their natural diet consists of hard-shelled gastropods and bivalves. A specialized feeding mechanism (pharyngeal jaw) forms a crushing surface used to grind prey. In aquaculture, extruded pellets are fed and this feeding apparatus results in pellets fracturing and loss of fragments through their gill rakers. The effect of pellet form (hard vs. soft) and size on fractured pellet waste (FPW) and production characteristics of Pompano reared in recirculating aquaculture systems was addressed. No difference in FPW between the standard pellet size and smaller pellet size treatments. However, a difference in FPW at first feeding of the day between the hard and soft pellet treatments was observed, with no difference in FPW present at the last feeding. Results suggest that pellet size does not reduce the amount of FPW produced, while the use of soft pellets reduces the amount of FPW.

Cultivation of microbial populations is a necessity for the use of microbes within the biotechnological and pharmaceutical industries, however, approximately only 1% of bacteria have been successfully cultivated in the lab. Dilution to Extinction (DTE) is a technique which involves serially diluting a microbial suspension to single cell inoculum prior to inoculation in a liquid medium designed to replicate natural aquatic environments. This technique was used here for the cultivation of diverse, potentially novel microbes from the marine sponge, Mycale microsigmatosa. One hundred thirty-six samples were successfully sequenced and identified with the majority belonging to the classes Alphaproteobacteria and Gammaproteobacteria. Furthermore, when combined with miniaturized fermentation, DTE allowed for the isolation and identification of marine natural products (3-Heptyl-3-hydroxy-2,4 (1H, 3H)-quinolinedione and 2-Heptyl-4-hydroxyquinoline) active against Methicillin-resistant Staphylococcus aureus. These metabolites originated from Pseudomonas aeruginosa, an isolate obtained from Mycale microsigmatosa using this technique.

Shellfish aquaculture “grow-out” sites for Northern Quahog (Mercenaria mercenaria) clams have substantially higher densities than the surrounding ambient environment and thus can attract local molluscivores to these areas. I used acoustic telemetry to examine potential interactions of two highly mobile ray species (cownose ray, whitespotted eagle ray) with two clam grow-out sites in the Indian River Lagoon near Sebastian, FL, where clammers have reported damaged grow-out gear. Visitation patterns of telemetered rays to these sites were compared to other reference sites in the region and modeled using local environmental data. While both species spent greater time elsewhere, I found many instances in which rays remained within range of clam grow-out sites for extended periods (>60 minutes). Mesocosm experiments with whitespotted eagle rays confirmed they were capable of interacting with and damaging clams housed within antipredator materials, although mortality was significantly reduced compared to controls and in particular by multi-layer netting.