Department of Marine Science and Oceanography

Microplastics are a ubiquitous pollutant that has emphasized major concern for several benthic ecosystems and for the species that inhabit them especially as temperatures have begun to warm at an exponential rate. This study has investigated the abundance and trophic transfer intensity of microplastics through exposure experimentation to two different benthal organisms, the stone crab (Menippe mercenaria) and hard clam (Mercenaria mercenaria), under three different temperature gradients. Within a laboratory setting, hard clams were exposed to a concentration of different sizes and types of microplastics in three different temperatures to observe the accumulation rate of these particles from direct ingestion. The exposed clams were then fed to predatory stone crabs from the Indian River Lagoon, under the same three temperature treatments, to detect MP trophic transfer. To examine the disposition of ingested plastics, histology and fluorescent microscopy were used to quantify the locations and numbers of microplastics in the tissues.

This study examined the effectiveness of a magnetic shark deterrent, the SharkBanz® Zeppelin, and quantified the magnetic field it produces. A shark entering the magnetic field induces an electric field that is detectable by electroreceptors. This novel stimulus may deter sharks away from hooked fish. The magnitude declined rapidly with distance and reached the ambient geomagnetic field at 36-39 cm away. Zeppelin devices and non-magnetic controls were deployed with baited remote underwater video systems, and the responses of sharks were recorded. There was a significant difference between the number of sharks deterred between the Zeppelin and control. The Zeppelin deterred sharks on 22% of their approaches in the effective range, whereas the control deterred them on 2.6% of their approaches. Although the device may be effective at deterring sharks and act as a mitigation strategy for shark depredation, tests with live fish that provide more sensory stimuli are needed.

The overall objective was to elucidate the effect of iron (Fe) on nitrogen (N) diagenesis in Lake Okeechobee. Somewhat counterintuitively, sediment ammonium (NH+4) inventories decreased during algal growth as dissolved organic nitrogen (DON) inventories increased. Whole core incubations were staged for denitrification experiments using isotopic N tracer. Core incubations showed the percentage of sediment N removal increase between summer (25 ± 21 %) and winter (39 ± 13 %). The amendment of Fe2+ enhanced this seasonal effect likely via dissimilatory nitrate reduction to ammonium (DNRA). The isotopic signature of N2 flux also suggested an additional, sedimentary, N2 source via Fe coupled anaerobic oxidation of ammonium (feammox). Sediment slurry incubations supported the occurrence of both DNRA and feammox, showing first that nitrate (NO3−) was converted to NH4+ via DNRA, which contributed 23-26% of overall NO3− reduction.
Fe amendment in slurries similarly stimulated the feammox process. However, aged Fe minerals accumulated linearly with N bound to Fe (Fe-N) in a subseasonal sediment time series, suggesting Fe-organic matter aggregation may lower the sediment NH4+ equilibrium concentration and benthic flux.

Antibiotic resistance is a growing concern due to the improper use of antibiotics. Not only is antibiotic resistance increasingly occurring in human populations, but it appears to be spreading in wildlife populations too due to drug overuse and misuse in medicine, farming, and industrial settings, and the subsequent release into watersheds. This project examined the prevalence of antibiotic resistant bacteria in the hindgut microbiome of green (Chelonia mydas) (n=60) and loggerhead (Caretta caretta) (n=57) sea turtles. Hindgut swabs were cultured for gram negative bacteria and exposed to 6 antibiotics. 83.3% of samples were resistant or intermediately resistant to at least one antibiotic, and 27.7% of samples were resistant or intermediately resistant to three antibiotics. This study provides more information regarding the relationship between turtle characteristics and the presence of antibiotic resistance in the hindgut of Florida sea turtles, as well as examine the types of bacteria found in the hindgut.

The distribution and intensity of hypoxia (low dissolved oxygen, DO) is increasing due to eutrophication and algal blooms in estuaries like those in the Gulf of Mexico and the Indian River Lagoon. The objective of this study is to determine how low DO affects the development and lipid utilization of the Florida Pompano (Trachinotus carolinus) and Red Drum (Sciaenops ocellatus). Fertilized eggs were incubated in two DO hypoxia treatments: severe (20% DO saturation, 1.6 mg/L), moderate (50% DO saturation, 3.9 mg/L), and normoxia (100% DO saturation, 7.6 mg/L). Eggs and larvae were sampled at 24-hours post-fertilization to assess hatch survival, larval development, and fatty acid (FA) lipids utilization. Results suggest hypoxia significantly impacts Florida Pompano development, with polar FAs most affected, while Red Drum shows greater tolerance to low DO. These findings provide insight into early fish larval stages to improve conservation and management strategies for their recruitment.

Impoundments in the Indian River Lagoon, originally built to control saltmarsh mosquitoes, led to the isolation of fish nursery habitats. Rotational Impoundment Management (RIM) aims to mitigate this by hydrologically reconnecting impoundments during mosquito non-breeding seasons. However, current practices may not effectively facilitate juvenile fish emigration. This study incorporates summer openings (drawdowns) of culverts into RIM to improve the emigration of juvenile tarpon and snook. Tagged fish were monitored with RFID technology for 18 months in four impoundments. The abundance and size distribution of tarpon and snook populations differed among impoundments, reflecting variations in habitat structure and water quality. Summer drawdowns did not significantly increase emigration rates. However, tarpon detections increased during closed-culvert periods in all impoundments, and snook detections increased in one impoundment. Despite low emigrations, the study offers insight into the behavior of juvenile fish in these impoundments and suggests ways to enhance their nursery functionality.

Iron and manganese redox chemistry are important drivers of sulfur cycling in marine sediments. Florida Bay sediments are extremely sulfidic, having been attributed to mass mortality of seagrass and oxygen depletion in the water column. This research used conventional sediment analyses and a diagenetic model to infer the overall capacity for Florida Bay sediments to eliminate hydrogen sulfide and prevent high rates of sediment dissolved oxygen consumption via hydrogen sulfide reoxidation. Previous studies have suggested that iron is important for buffering hydrogen sulfide in Florida Bay sediments, while the results of this project show for the first time that this phenomenon is relevant only in specific locations and times of the year. However, my research indicates that Fe has the potential to sequester sulfides and minimize hypoxia in the Everglades system. Thus, under a scenario that greater amounts of Fe are delivered to Florida Bay sediments from freshwater flows under Everglades restoration, Fe could be a component of ecosystem management.

In the inter-coastal waters of Florida, green sea turtles (Chelonia mydas) are regularly exposed to regional blooms of harmful algae which produce biotoxins. A retrospective analysis was conducted on stranded green sea turtles along the Indian River Lagoon, FL, USA. Stranding, necropsy, and histopathology reports were analyzed for 40 juvenile turtles. Liver (N=40) and kidney (N=36) tissues were analyzed for a suite of 14 harmful algal bloom (HAB)-associated biotoxins. Thirty-four (85%) turtles tested positive for at least one biotoxin, including 21(53%) liver and 22(61%) kidney tissues. Statistically significant relationships were identified between the presence of common histopathological abnormalities and biotoxins of: melanomacrophage/hyperplasia and brevetoxin-3 (P=0.03) in liver tissues, and renal fibrosis and nodularin (P = 0.04) and lymphocytosis and neosaxitoxin (P=0.03) in kidney tissues. These data demonstrate that wild turtles are commonly exposed to HAB-associated biotoxins with potential chronic health effects that contribute to strandings in the Indian River Lagoon.

Existing brood fish research has ascertained that eggs are heavily influenced by broodstock diet but there is no information regarding this timeline of nutritional incorporation. The objective of this study is to determine duration of nutritional incorporation from diet to eggs through fatty acids. Nine California Yellowtail (Seriola dorsalis) broodstock were fed alternating diets of commercial pellets (Vitalis PRIMA: Skretting) and cutbait. Biochemical and biometric data from spawns were collected and analyzed for differences and similarities throughout the alternating diets. Eggs were observed to selectively incorporate higher sources of linolenic and linoleic acid from the pelleted diet, and eicosapentaenoic acid from the cutbait diet. Interestingly, results showed overall fatty acids from both diets were fully incorporated by eggs within 9 days following the diet switch. These findings provided new insight towards the selective incorporation of nutrients and will open new doors for future broodstock nutrition research.

The Deepwater Horizon Oil Spill had widespread impacts that were seen across the surface of the ocean, deep-sea, and seafloor. To assess damages, NOAA and GoMRI established the Offshore Nekton Sampling and Analysis Program (ONSAP) and the Deep Pelagic Nekton Dynamics of the Gulf of Mexico (DEEPEND) projects. This response effort would create a vast dataset and collection of samples to aid in understanding the deep-sea of the northern Gulf of Mexico.
Genus Melamphaes (Family Melamphaidae), are a group of minimally characterized and understudied fish. This thesis will assess vertical ecology and migratory patterns, variations in specimen size and sampling gear, and introduce species that are newly identified to inhabit the area. The findings suggest that majority of Melamphaes participate in diel vertical migration and sampling equipment has significant impacts on specimen size. Four unreported species of Melamphaes have now been documented in this region, increasing previously reported diversity.