Chelonia mydas

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.

Fibropapillomatosis (FP) is a tumor disease that has reached panzootic proportions in green turtles (Chelonia mydas). FP is associated with chelonid alphaherpesvirus 5, although the etiology of FP is likely multifactorial, since high FP prevalence is often observed in degraded habitats. However, specific environmental cofactors for tumor development remain unknown. To explore this, I collated statewide green turtle stranding data from 2000–2020 to evaluate spatiotemporal trends of FP in Florida, and co-analyzed these data alongside patterns of river flow, chlorophyll-a (Chla), sea surface temperature (SST), El Niño (ENSO), and red tide (HAB). I found that FP was stable during 2000–2020. HAB (positively) and SST (negatively) correlated with statewide FP prevalence, as well as several interactions between various factors. These results suggest that SST and HABs may act as cofactors in the development of FP, and future work should be equally interdisciplinary in their investigation of this multifactorial disease

Green sea turtles (Chelonia mydas) are an endangered species prone to a debilitating disease called fibropapillomatosis (FP). The aim of this study was to determine the influence of UV light on vitamin D levels and immune function in juvenile green sea turtles with FP. Phagocytosis, plasma vitamin D levels and viral load of ChHV5 were measured for FP- and FP+ turtles kept at the Gumbo Limbo Nature Center (GLNC) and for turtles caught at the St. Lucie power plant. Turtles kept at GLNC were housed in tanks exposed to varying amounts of UV light. Turtles brought into GLNC had lower phagocytosis compared to turtles at the St. Lucie power plant. Individuals exposed to greater UV light had higher plasma vitamin D levels and a more successful recovery. The results of this project will provide rehabilitation facilities with a mechanism to improve the recovery of animals with this disease.

Stable isotope analysis is a powerful tool that can be used to describe a population’s foraging niche by identifying basal resource use, trophic feeding levels, environmental stability, seasonal ecological variation, important shifts in life history, ontogenetic shifts, intraspecific habitat use, and population dynamics. Describing these relationships in endangered marine turtle populations and their critical foraging grounds is essential for determining informed management decisions. This study systematically describes the foraging niche of hawksbills Eretmochelys imbricata, and green turtles, Chelonia mydas in Buck Island Reef National Monument, U.S. Virgin Islands, a critical habitat for nesting and foraging. It assesses the relationships within and between the species in terms of overlap, annual and seasonal variation, and life history and feeding strategies within the community. Most importantly it describes these relationships with metrics that can be used in global comparisons or to measure change in local conditions.

Climate change has the potential to expose sea turtle nests to higher temperatures, which may negatively impact sea turtle hatchling vigor. In this study, loggerhead and green hatchlings were sampled from the Boca Raton, Florida beach and via lab incubation, and hatchling vigor was determined. Elevated nest temperatures decreased loggerhead and green turtle hatchling performance and corticosterone levels, with the most significant effects found in hatchlings exposed to maximum incubation temperatures above 35°C during late development. Lab-incubated loggerhead post-hatchling corticosterone levels and growth rates were also determined. The differences seen in corticosterone levels with overall nest incubation temperatures, mean temperatures during early, middle or late stages of development, and its negative correlation with hatchling performance improves our understanding of the underlying physiological mechanisms linking elevated incubation temperatures and sub-lethal physiological effects that may significantly impact hatchling survival, a critical step for sea turtle conservation in south Florida and elsewhere.

Hatchling marine turtles use visual cues to orient from their nest to the sea at
night. However, the wavelengths of light that carry this information have not been
properly documented, nor do we understand why they are favored. I measured
wavelength irradiance at 20 nm intervals between 340 – 600 nm at a dark nesting beach
and then, in the laboratory, determined the thresholds of the hatchlings for each λ that
evoked a positive phototaxis. In this study, I show that green turtle hatchlings are (i) most
sensitive to the shorter (360 – 480 nm) light wavelengths. Those light energies (ii)
dominated the available natural lighting at the nesting beach. They also (iii) presented a
steep gradient in irradiance between a landward and seaward view, an important cue for
orientation. I attribute the phototactic responses to “stimulus filtering”, the outcome of
natural selection that optimizes behavioral responses (seafinding) according to their
function, as well as when and where they occur.