Trace element bioaccumulation, tissue distribution, and elimination in odontocetes stranded in Florida and Georgia, USA over a 15-year period (2007-2021).

Odontocetes obtain nutrients including essential elements through their diet and are exposed to heavy metal contaminants via ingestion of contaminated prey. We evaluated the prevalence, concentration, and tissue distribution of essential and non-essential trace elements, including heavy metal toxicants, in tissue (blubber, kidney, liver, skeletal muscle, skin) and fecal samples collected from 90 odontocetes, representing nine species, that stranded in Georgia and Florida, USA during 2007-2021. Samples were analyzed for concentrations of seven essential (cobalt, copper, iron, manganese, molybdenum, selenium, zinc) and five non-essential (arsenic, cadmium, lead, mercury, thallium) elemental analytes using inductively-coupled plasma mass spectrometry. Risso's dolphins (Grampus griseus) and short-finned pilot whales (Globicephala macrorhynchus) had the highest median concentrations of mercury, cadmium, and lead, while dwarf sperm whales (Kogia sima) had the lowest. Adult pygmy and dwarf sperm whales that stranded in 2019-2021 had higher concentrations of arsenic, copper, iron, lead, manganese, selenium, thallium, and zinc compared to those that stranded in 2010-2018, suggesting an increasing risk of exposure over time. The highest concentrations of many elements (e.g., cadmium, cobalt, copper, manganese, molybdenum, thallium, zinc) were in fecal samples, illustrating the usefulness of this noninvasively collected sample. Aside from fecal samples, hepatic tissues had the highest concentrations of iron, manganese, mercury, molybdenum, and selenium in most species; renal tissues had the highest concentrations of cadmium; skin had the highest concentrations of zinc; and copper, arsenic, and lead concentrations were primarily distributed among the liver and kidneys. Phylogenetic differences in patterns of trace element concentrations likely reflect species-specific differences in diet, trophic level, and feeding strategies, while heterogeneous distributions of elemental analytes among different organ types reflect differences in elemental biotransformation, elimination, and storage. This study illustrates the importance of monitoring toxic contaminants in stranded odontocetes, which serve as important sentinels of environmental contamination, and whose health may be linked to human health.

A case study of monofilament line entanglement in a common bottlenose dolphin (Tursiops truncatus): entanglement, disentanglement, and subsequent death.

BACKGROUND: Free-ranging common bottlenose dolphins (Tursiops truncatus) can become entangled in fishing line and other marine debris. Infrequently, dolphins can be successfully disentangled, released back into the wild, and later examined postmortem to better understand the pathology and long-term effects of these entanglements. CASE PRESENTATION: An entangled common bottlenose dolphin (Tursiops truncatus) calf was observed in the Indian River Lagoon, Florida, USA, with monofilament fishing line wrapped tightly around its maxilla. A multi-agency team successfully disentangled the dolphin for immediate release back into its natural habitat. A year after disentanglement, photos and observations indicated that the now independent calf showed a decline in body condition, characterized by grossly visible ribs and a prominent post-nuchal depression. More than 2 years post-disentanglement, the freshly dead carcass of this juvenile dolphin was recovered with extensive predation wounds. Despite the forestomach being ~ 50% full of ingesta (fish), the dolphin was emaciated. During postmortem examination, we collected and evaluated photographs and measurements of the maxillary damage resulting from the entanglement. CONCLUSION: The monofilament entanglement caused permanent, bilateral deformation of the maxillary dental arcade, including a 4.0-4.2 cm long, 0.5 cm deep linear groove where the entanglement eroded the lateral edges of the maxilla. There was no evidence of maxillary fracture and the dolphin survived for more than 2 years after disentanglement. External evidence of propeller scars and a fishing hook discovered embedded in the laryngeal mucosa at necropsy indicated repeated human interactions.

Tumor re-growth, case outcome, and tumor scoring systems in rehabilitated green turtles with fibropapillomatosis.

Fibropapillomatosis (FP) is an infectious, neoplastic disease of major concern in sea turtle rehabilitation facilities. Rehabilitating sea turtles that undergo tumor removal surgery often have tumor regrowth and may experience mortality. We evaluated tumor score, removal, and regrowth in rehabilitating green sea turtles with FP in 4 rehabilitation facilities in the southeastern USA during 2009-2017. Of 756 cases, 312 (41%) underwent tumor removal surgery, 155 (50%) of those had tumor regrowth within an average of 46 ± 45 d, and 85 (27%) had multiple (>1) regrowth events. Of 756 turtles with FP, 563 (75%) did not survive after admission into a rehabilitation facility, including 283 (37%) that were euthanized and 280 that died without euthanasia (37%), and 193 survived, including 186 (25%) released and 7 (1%) placed in permanent captive care. Tumor removal surgery increased the odds of tumor regrowth but also enhanced survivorship, whereas tumor regrowth was not a significant predictor of case outcome. Three FP tumor scoring systems were used to assign tumor scores to 449 cases, and differing results emphasize that tumor scoring systems should be applied to the situations and/or location(s) for which they were intended. FP tumor score was not a significant predictor for the event or extent of FP tumor regrowth after surgical excision. Under current rehabilitation regimes, outcomes of rehabilitation for tumored turtles have a low probability of success. The results of this study may be used to help guide clinical decision-making and determine prognoses for rehabilitating sea turtles with FP.

Terrestrial basking sea turtles are responding to spatio-temporal sea surface temperature patterns.

Naturalists as early as Darwin observed terrestrial basking in green turtles (Chelonia mydas), but the distribution and environmental influences of this behaviour are poorly understood. Here, we examined 6 years of daily basking surveys in Hawaii and compared them with the phenology of local sea surface temperatures (SST). Data and models indicated basking peaks when SST is coolest, and we found this timeline consistent with bone stress markings. Next, we assessed the decadal SST profiles for the 11 global green turtle populations. Basking generally occurs when winter SST falls below 23°C. From 1990 to 2014, the SST for these populations warmed an average 0.04°C yr(-1) (range 0.01-0.09°C yr(-1)); roughly three times the observed global average over this period. Owing to projected future warming at basking sites, we estimated terrestrial basking in green turtles may cease globally by 2100. To predict and manage for future climate change, we encourage a more detailed understanding for how climate influences organismal biology.