Department of Marine Science and Oceanography

This study explored spatiotemporal patterns in movement, diet, and baseline phycotoxin concentrations in immature bull sharks (Carcharhinus leucas) of the Indian River Lagoon (IRL), an estuary of national significance that has been considerably impacted by multiple toxic harmful algal blooms (HABs). Long-term spatial use of the system was assessed for 29 acoustically tagged sharks over a 4 year period (2017–2020). Tissue samples for diet and toxin analysis were collected from a separate cohort of 50 individuals between 2018 and 2020. UPLC-MS/MS was used to screen tissues for 14 algal toxins. Young bull sharks were found to be mainly piscivorous and displayed high residency to the IRL as well as to specific regions of the IRL, with small activity spaces. Multiple phycotoxins were detected in screened tissues, indicating that young bull sharks in the IRL may be compromised by trophic transfer of HABs while they reside in this important nursery.

The sunray venus (SRV) clam (Macrocallista nimbosa), is an alternative shellfish aquaculture species to hard clams (Mercenaria mercenaria) for Florida. Production of high-quality hatchery seed is dependent on diet. This study was initiated to determine an optimal live microalgae diet and test the efficacy of commercially available microalgae concentrates as partial or complete replacements for live algae. Benefits were seen with multiple algal species combinations. Both clam species achieved highest growth and survival when fed a multi-species quad-algal live diet, although hard clams performed well when fed I. galbana and C. gracilis or I. galbana and P. lutheri. Neither species performed well with complete replacement diets, but showed good production with partial replacement diets. The fatty acid (FA) profile of clams reflected the FA profile of the fed diet. Clams fed multi-species diets of live algae had a well-balanced FA profile consisting of high n3/n6, EPA/DHA and EPA/ARA ratios.

Harmful organic contaminants, such as petroleum hydrocarbons, are ubiquitous in coastal marine ecosystems around the world, a problem that will only be exacerbated with rising sea level and increased inundation of coastal urban areas. Therefore, it is necessary to understand the fate of these contaminants following their deposition on marine sediment, where they can potentially persist for long periods of time. As organic carbon remineralization rates depend on the respiration process employed by the bacteria in the sediment, it was the goal of this study to determine how the sediment redox environment, with an emphasis on Fe redox chemistry, affects the biodegradation of recalcitrant petroleum hydrocarbon compounds. While amendment of natural sediment with Fe minerals that are commonly transported to coastal areas following erosion from continental crust did successfully catalyze Fe reduction and inhibit sulfate reduction, the effect on the hydrocarbon biodegradation rate was negligible. However, inoculation of the sediment with Shewanella oneidensis, an exoelectrogenic, Fe reducing bacteria known to catalyze the degradation of hydrocarbon compounds found in crude oil, did
significantly affect the redox environment and sediment microbial communities and alter the pattern of hydrocarbon loss in the sediment over time.

The leatherback sea turtle (Dermochelys coriacea) is facing global declines; however, the Florida stock is generally increasing. Various studies have identified threats to sea turtles, but there is a need to quantify population-level threats. I used external examination and blood analyses of leatherbacks nesting on northern Palm Beach County, Florida beaches to understand the impact(s) that physical injuries have on this population. Notable injuries were present on 118 of 167 (70.7%) turtles. Fisheries injuries were more prevalent than other anthropogenic injuries; however, there was a higher overall prevalence of natural injuries. There were no notable findings from my blood analyses. My results suggest that while natural injuries are more common than anthropogenic injuries in the nesting population of Florida leatherbacks, anthropogenic injuries are more likely to result in severe traumatic wounds. Future investigation of overlap in leatherback migratory routes and foraging grounds with various threats could further protect this species.

The Indian River Lagoon (IRL) spans approximately one-third of the east coast of Florida and faces numerous harmful algal blooms. The potentially toxic diatom, Pseudonitzschia, has been observed in many locations of the IRL. The goal of this study was to obtain a better understanding of the factors contributing to population dynamics of Pseudo-nitzschia in the southern IRL system. Bi-monthly surface water samples were collected for 18 months from five locations. Cell counts enumerated all microphytoplankton, and environmental data was collected at sampling sites throughout the study by the Indian River Lagoon Observatory Network. Six species of Pseudonitzschia were isolated and characterized through 18S Sanger sequencing and scanning electron microscopy, all showed toxicity. Surface water samples also showed domoic acid (DA) presence. We report the first known occurrence of Pseudo-nitzschia micropora in the IRL and the first known DA production from this taxon.

Marine sponges are economically and environmentally valuable, but restoration, commercial, and biomedical demands exceed what wild populations and aquaculture can provide. In vitro culture of sponge cells is a promising alternative, but has remained elusive until recent breakthroughs involving improved nutrient medium M1 in two-dimensional culture. The advantages of three-dimensional over two-dimensional cell culture have been increasingly recognized. Here we report the successful 21-day culture of cells from the marine sponge Geodia neptuni using multiple three-dimensional cell culture methods: FibraCel© disks, thin hydrogel layers, gel micro droplets, and spheroid cell culture. These methods performed comparably to two-dimensional control cultures, and each method offers advantages for restoration or in vitro applications using sponge cells. Further optimization of these methods may lead to the ability to culture fully functioning sponges from dissociated, cryopreserved cells, which will reduce the need for wild harvest of sponge tissues for commercial, restoration, and biomedical purposes.