Prevalence of algal toxins in Alaskan marine mammals foraging in a changing arctic and subarctic environment

Abstract

Current climate trends resulting in rapid declines in sea ice and increasing water temperatures are likely to expand the northern geographic range and duration of favorable conditions for harmful algal blooms (HABs), making algal toxins a growing concern in Alaskan marine food webs. Two of the most common HAB toxins along the west coast of North America are the neurotoxins domoic acid (DA) and saxitoxin (STX). Over the last 20 years, DA toxicosis has caused significant illness and mortality in marine mammals along the west coast of the USA, but has not been reported to impact marine mammals foraging in Alaskan waters. Saxitoxin, the most potent of the paralytic shellfish poisoning toxins, has been well-documented in shellfish in the Aleutians and Gulf of Alaska for decades and associated with human illnesses and deaths due to consumption of toxic clams. There is little information regarding exposure of Alaskan marine mammals. Here, the spatial patterns and prevalence of DA and STX exposure in Alaskan marine mammals are documented in order to assess health risks to northern populations including those species that are important to the nutritional, cultural, and economic well-being of Alaskan coastal communities. In this study, 905 marine mammals from 13 species were sampled including; humpback whales, bowhead whales, beluga whales, harbor porpoises, northern fur seals, Steller sea lions, harbor seals, ringed seals, bearded seals, spotted seals, ribbon seals, Pacific walruses, and northern sea otters. Domoic acid was detected in all 13 species examined and had the greatest prevalence in bowhead whales (68%) and harbor seals (67%). Saxitoxin was detected in 10 of the 13 species, with the highest prevalence in humpback whales (50%) and bowhead whales (32%). Pacific walruses contained the highest concentrations of both STX and DA, with DA concentrations similar to those detected in California sea lions exhibiting clinical signs of DA toxicosis (seizures) off the coast of Central California, USA. Forty-six individual marine mammals contained detectable concentrations of both toxins emphasizing the potential for combined exposure risks. Additionally, fetuses from a beluga whale, a harbor porpoise and a Steller sea lion contained detectable concentrations of DA documenting maternal toxin transfer in these species. These results provide evidence that HAB toxins are present throughout Alaska waters at levels high enough to be detected in marine mammals and have the potential to impact marine mammal health in the Arctic marine environment.

Trends and Carrying Capacity of Sea Otters in Southeast Alaska

“…In addition to density‐dependent population regulation, density‐independent factors can play significant roles in driving sea otter population trends. Density‐independent factors can include environmental stressors (e.g., red tides or other harmful algal bloom events; Kvitek and Bretz , Lefebvre et al ), certain infectious disease outbreaks (Johnson et al , Goldstein et al ), inter‐specific interactions (e.g., predation mortality from killer whales [ Orcinus orca ] or white sharks [ Carcharodon carcharias ]; Estes et al , Tinker et al ), and anthropogenic factors, including oil spills (Monson et al a , ; Bodkin et al ) and direct human harvest. Our results suggest that human harvest may be affecting trends in some sub‐regions of Southeast Alaska, particularly long‐established areas where mean annual harvest rates exceed 10% of population size (with some years as high as 20%; Table S4).…”

Chronic low-level exposure to the common seafood toxin domoic acid causes cognitive deficits in mice

“…The prevalence of domoic acid (DA) in seafood products is likely to increase as DA- producing algal blooms continue to become more frequent, more toxic, longer-lasting and cover larger geographic areas (Lefebvre et al, 2016; McCabe et al, 2016; Moore et al, 2008; Van Dolah, 2000). Current seafood safety regulations for the United States and the European Union target single high-level DA exposure and have been effective at protecting seafood consumers from acute high level DA exposure characterized by seizures, memory loss and brain lesions.…”

Year-round algal toxin exposure in free-ranging sea lions

“…Scat subsamples were analyzed using direct competitive enzyme-linked immunosorbent assays (ELISA) following methods described by Lefebvre et al (2016). Domoic acid was analyzed using ASP direct cELISA kits (Biosense Laboratories).…”

“…Few publications have attempted to compare or validate the saxitoxin ELISA in marine mammal feces or tissues with other methods, although some authors have performed matrix testing to avoid false positives or negatives (e.g. Lefebvre et al 2016). Due to the limited-cross reactivity with other PST toxins, we must assume that the saxitoxin ELISA potentially underestimated the full sample toxicity.…”