Toxic elements found in stranded whales, dolphins over 15 years

Dolphins and whales stranded along the southeast coast of the United States have been found to have elevated levels of toxins. Monitoring toxic pollutants in these stranded marine animals, which act as important sentinels of environmental pollution, and whose health may be linked to human health, is critical.

Nevertheless, data are scarce on how specific elements are distributed within an animal’s body, especially for many rarely encountered species, and toxicity levels vary by sex. , related to race, age and other demographic factors.

A study by a team of scientists led by Florida Atlantic University’s Harbor Branch Oceanographic Institute examined the prevalence, concentration, and tissue distribution of essential and nonessential trace elements, including tissue heavy metal toxins (bulbar , kidney, liver, skeleton) muscle, skin) and gut samples were collected from 90 whales and dolphins stranded in Georgia and Florida from 2007 to 2021.

The researchers analyzed 319 samples from nine species for trace amounts of seven essential (cobalt, copper, iron, manganese, molybdenum, selenium, zinc) and five non-essential (arsenic, cadmium, lead, mercury, thallium) trace elements. All species in the study occupied high and similar trophic levels and ate a mixture of cephalopods and fish.

The results of the study, published in the journal Cell Press: Helionshowed that Reso’s dolphin (Grampus griseus) and the short pin pilot wheel (Globicephala macrohunches) had the highest median concentrations of mercury, cadmium and lead, while dwarf sperm whales (Kogya Seema) was the lowest.

Adult pygmy and pygmy sperm whales stranded from 2019 to 2021 had higher concentrations of arsenic, copper, iron, lead, manganese, selenium, thallium and zinc than those stranded from 2010 to 2018, which is Indicates increased risk of exposure over time.

“When we separated the phylogenetic groups into age classes and compared the median concentrations of heavy metals in specific tissue types between mature specimens of the species, we found some interesting trends,” said Annie Page, DVM, Ph.D. said D, senior author, a research associate. Professor and Clinical Veterinary, FAU Harbor Branch.

Many elements (eg, cadmium, cobalt, copper, manganese, molybdenum, thallium, zinc) had the highest concentrations in intestinal samples, illustrating the utility of this noninvasively collected sample.

Except for intestinal samples, liver or liver tissue had the highest concentrations of iron, manganese, mercury, molybdenum and selenium in most species. The kidneys or kidney tissues had the highest amount of cadmium; Skin had the highest zinc content; And copper, arsenic and lead concentrations were mainly distributed in the liver and kidneys.

The lowest median concentrations of mercury and cadmium were in liver, kidney, bulbar, and muscle samples, with the lowest skin mercury concentrations and the lowest liver lead concentrations from dwarf sperm whales.

Mercury is one of the most toxic elements in marine systems and can bioaccumulate and biomagnify through marine food webs. Cetaceans are exposed to mercury and other toxic metals mostly through consumption of contaminated prey items, which tend to accumulate mercury in the liver, muscles and other tissues over time.

“Exposure to heavy metal pollutants can result in oxidative stress, which can impair protein function, damage DNA and disrupt membrane lipids,” Page said. “Heavy metal exposure has been linked to heart disease, immunodeficiency and increased parasite infections, among other disease risks.”

Results from the study provide important baseline data needed to further evaluate the pathophysiological mechanisms and environmental risks associated with exposure and accumulation of trace elements in tissues of free-ranging whales and dolphins.

“Because tissue concentrations of heavy metal contaminants also vary based on an individual animal’s sex, age class, trophic level, and location, among other factors, it is important to first establish baseline values ​​and then quantify these toxicants. Continue to monitor cetacean populations for exposure,” the page said.

Among the species examined in the study were pygmy sperm whales (Kogia breviceps); dwarf sperm whale; Gervais’ beaked whale (Mesoplodon europaeus); the dolphin of Russo; Short pilot whale sperm whale (Physiator macrocephalus); Melon-head whale (Paponocephala electra); Blainville’s beaked whale (Mesoplodon densirostris); and a false killer whale (A pseudo-arc thickening).

Study co-authors represent the FAU Harbor Branch; US Coast Guard Academy; University of Alabama at Birmingham; Hubbs-Sea World Research Institute; Blue World Research Institute; Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute; and the Georgia Department of Natural Resources.

This work was supported by the Florida State License Plate Program “Protect Wild Dolphins” and “Protect Florida Whales” grants (administered by the Harbor Branch Oceanographic Institute Foundation). Link Foundation; John H. Prescott Marine Mammal Rescue Assistance Grant; SeaWorld Bush Gardens Conservation Fund; Discover the Florida Oceania license plate. and the Brevard County Tourism and Development Council.