Dr. Alexis M Janosik

Microplastics, remnants of macroplastics that have broken down to fragments smaller than 5 mm, and nanoplastics, broken down even further to sizes < 1 μm, are pervasive in aquatic ecosystems. These plastic particles are consumed by microscopic organisms, leading to bioaccumulation up trophic levels. The accumulation of plastic in the organismal gut can result in various repercussions, including cellular contamination and genomic modifications such as DNA methylation. While methylation has been studied in teleost fishes, the impact of nanoplastic exposure on this process in any species remains largely unexplored. This study delves into this largely uncharted territory, investigating the accumulation of methylation due to nanoplastic exposure within the genome of cultured bluegill BF-2 cells (Lepomis macrochirus) using methylation-sensitive AFLPs. The methylation state was analyzed through capillary gel analysis and electropherograms. Differential methylation occurred between several control and experimental groups due to nanoplastic exposure; however, these differences were not dose- or time-dependent. These results could suggest that higher dosages and exposure times to nanoplastics do not result in increased methylation levels in congruence with the dosage and exposure time; rather, only the presence of nanoplastics is enough to cause DNA methylation changes.

Microplastics, small pieces of plastic measuring less than five millimeters, have spread to all ecosystems, even those in the Southern Ocean around Antarctica. In particular, microplastics have been found contaminating water in emerging fjords, or inlets created by deglaciation, along the Antarctic Peninsula. Microplastics contamination puts fjord communities, which are unique and dominated by benthic species, at high risk for microplastic exposure leading to issues with feeding, endocrine disruption, and exposure to adsorbed toxins, all of which lower fecundity and survivability. The objective of this study was to quantify microplastics in invertebrates grouped according to feeding type. Invertebrates were collected from the Western Antarctic Peninsula fjords during 2017 and 2020 from three fjords via a mini-Agassiz trawl to quantify microplastic concentrations and identify polymer composition using Micro-ATR-FTIR. In 2017, 2.39 microplastics individual−1 were identified, while 5.01 microplastics individual−1 were identified in 2020. Out of the 24 polymers and polymer associates identified, the most common polymers were polypropylene, polycarbonate, polyamide, and polystyrene. Overall, the most common microplastic color category was black/brown/Gy, and fragments were the most common shape identified. Microplastics presence was significantly higher in the invertebrate organisms compared to procedural blanks (p < 0.001), but feeding mechanism was not found to be a predictor of microplastic bioaccumulation. Microplastics concentrations in invertebrates differed between fjords in 2017 (p = 0.010) but not in 2020. Complementing previous research on microplastics in Southern Ocean fjordic water, this study reveals new evidence of microplastics in Antarctic fjordic inhabitants.

Environmental DNA (eDNA) metabarcoding is a novel molecular tool that is used to detect and catalog biodiversity from remnant DNA in the environment, including at-risk and elusive species. We used eDNA metabarcoding in this study to detect the spatiotemporal occurrence of River Redhorse (Moxostoma carinatum) and catalog the fish community in the Escambia-Conecuh River system of Florida and Alabama, hereafter referred to as the Escambia River system. The River Redhorse is a catostomid that has been classified as a Species of Greatest Conservation Need in Florida, as only three specimens have been collected from the Escambia-Conecuh River system in the last 70 years. In Alabama, only 20 specimens have been collected from this system since 2000. Surface water samples were collected at sites from the Escambia River system in December 2020 and March to June 2021. Universal MiFish primers were used and detected 47 fish species across sampled seasons from collected water samples, including River Redhorse. River Redhorse DNA was detected in high frequencies in all sampling seasons. The high occurrence of River Redhorse DNA across sampled localities provides evidence that the population is extant in the Escambia-Conecuh River system. Detections provide ideal spatiotemporal locations for conventional sampling methods to be deployed to gather essential biological data for the conservation and management of the River Redhorse. In addition, the metabarcoding approach cataloged the fish community temporally in the Escambia River System, indicating its usefulness as a complementary approach to conducting fish surveys with conventional sampling methods.

A complete picture of diet composition is an essential element to understanding the ecological role of organisms. Moreover, diet studies can serve as an important tool for monitoring species and changes to the food web. One method to provide resolution when studying the diet of avian species is DNA metabarcoding of fecal samples. As such, we used DNA analysis to determine the diet of the Least Tern Sternula antillarum and compare results with diet analysis based on composition of fish dropped within breeding colonies. Comparisons between adult and chick fecal samples were also made across three years and within three zones of sample collection. Results show differences in diet composition between the two methods as well as across zones and years. Significant differences between prey items of adults and chicks were also identified. Metabarcoding data indicate that Least Terns are consuming Lionfish Pterois spp. (most likely in larval stages), a prey item that had not been previously recorded for Least Terns, and that data obtained from dropped fish might not be representative of chick diet. Differences across years and zones are likely due to shifts in the abundance and availability of prey items.

Complementary approaches (stomach contents, DNA barcoding, and stable isotopes) were used to examine seasonal shifts in the feeding ecology of an oceanic predator, yellowfin tuna (Thunnus albacares, n = 577), in the northern Gulf of Mexico. DNA barcoding greatly enhanced dietary resolution and seasonally distinct prey assemblages were observed for both sub-adults and adults. In general, diet was characterized by ommastrephid squids and exocoetids in spring, juvenile fishes (i.e., carangids and scombrids) in summer, migratory coastal fishes during fall, and an increased consumption of planktonic prey (e.g., amphipods) in winter. Seasonal variability in bulk stable isotope values (δ13C, δ15N, and δ34S) was also observed, with low δ15N values and high δ34S values during late summer/early fall and high δ15N values (low δ34S) during late winter/early spring. Bayesian stable isotope mixing models corroborated seasonal diet shifts, highlighting the importance of oceanic nekton in spring/summer, coastal nekton during fall, and oceanic plankton during winter. Seasonal shifts in diet appeared to be influenced by prey reproductive cycles, habitat associations, and environmental conditions. Findings highlight the complex food web dynamics supporting an opportunistic oceanic predator and the importance of seasonal cycles in prey availability to predator resource utilization in open-ocean ecosystems.

Sea turtles, in comparison with marine mammals, sea birds, and fishes, are the most affected by microplastics in terms of number of individuals impacted and concentration within each organism. The ubiquitous nature and persistence of microplastics in the environment further compromises sea turtles as many species are currently vulnerable, endangered, or critically endangered. The objective of this study was to quantify microplastic contamination in unviable loggerhead sea turtle eggs (Caretta caretta). Eggs were collected from seven locations along the northwest coast of Florida. A total of 70 nests and 350 eggs were examined. Microplastics (n = 510) were found in undeveloped loggerhead sea turtle eggs across all seven sites, suggesting that maternal transference and/or exchange between the internal and external environment were possible. The frequency found was 7.29 ± 1.83 microplastic pieces per nest and 1.46 ± 0.01 per egg. Microplastics were categorized based on color, shape, size, and type of polymer. The predominant color of microplastics were blue/green (n = 236), shape was fibers (n = 369), and length was 10-300 μm (n = 191). Identified fragments, films, beads and one foam (n = 187) had the most common area of 1-10 μm
(n = 45). Micro-Fourier Transform Infrared (μ-FTIR) spectroscopy analysis demonstrated that polyethylene (11 %) and polystyrene (7 %) were the main polymer types. For the first time microplastics were found in unviable, undeveloped loggerhead sea turtle eggs collected in northwest Florida. This work provides insight into the distribution patterns of microplastic pollutants in loggerhead sea turtle eggs and may extend to other species worldwide.

Artificial reefs act as islands of biodiversity that provide substrate where sessile organisms can settle and mobile invertebrates and fishes can find shelter and food. Though these structures are common and widespread in the Gulf of Mexico, their community composition is not well understood. We aimed to ameliorate understanding of the invertebrate communities living on artificial reefs in the northeastern Gulf of Mexico by using molecular techniques and morphological examination to describe the biodiversity and genetic connectivity of crabs (Infraorders Anomura and Brachyura) living on and among artificial reefs near Pensacola, FL, USA. Specimens (N = 1,241) were collected from six artificial reefs using Autonomous Reef Monitoring Structures (ARMS) after four, six, and ten months of submergence, respectively, and were identified using DNA barcoding and morphological examination. Spatial and temporal trends in biodiversity were examined by comparing Hill-Shannon and Hill-Simpson diversities, richness, and canonical correspondence analysis. Population genetic analyses were performed on the two most commonly recovered species, Pseudomedaeus agassizii (A. Milne-Edwards, 1880) and Hexapanopeus paulensis (Rathbun, 1930). A total of 11 taxa were identified, and artificial reef shape was found to be influential in shaping spatial patterns of biodiversity. Species turnover was common across the ten months of sampling, and richness peaked at the ten-month mark. Population genetics revealed that there is high gene flow between the six sampling locations. This study is the first to describe the biodiversity of crab communities on artificial reefs in the northeastern Gulf of Mexico.