Study details toxic elements found in stranded whales, dolphins over 15 years

Whales and dolphins obtain nutrients and essential elements through their diet. While eating fish, squid, octopus, crustaceans and other marine mammals, they are also exposed to heavy metal pollutants.

Elevated levels of toxins have been found in stranded dolphins. The wheel Along the southeast coast of the United States. 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 ( Bladder, kidney, liver, Muscles attached to structuresvol.) and Intestinal samples 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 Hellionshowed that Reso’s dolphins (Grampus griseus) and short-finned pilot whales (Globicephala macrorhynchus) had the highest mean concentrations of mercury, cadmium and lead, while dwarf sperm whales (Kogia sima) had 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, the time of appearance. Also indicates an increased risk of exposure. .

“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 tissues 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 affect membrane lipids,” Page said. 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 the 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, it is important to first establish baseline values ​​and then estimate exposure to these toxicants. So continue to monitor cetacean populations, Page said.

The species examined in the study were the pygmy sperm whale (Kogia breviceps); dwarf sperm whale; Gervais’ Beaked Whale (Mesoplodon europaeus); the dolphin of Russo; short pilot whale sperm whale (Fyster macrocephalus); Melon whale (Peponocephala electra); Blaineville’s beaked whale (Mesoplodon densirostris); and a false killer whale (Pseudorca crassidens).