Ice seals as sentinels for algal toxin presence in the Pacific Arctic and subarctic marine ecosystems

Abstract

Domoic acid (DA) and saxitoxin (STX)‐producing algae are present in Alaskan seas, presenting exposure risks to marine mammals that may be increasing due to climate change. To investigate potential increases in exposure risks to four pagophilic ice seal species (Erignathus barbatus, bearded seals; Pusa hispida, ringed seals; Phoca largha, spotted seals; and Histriophoca fasciata, ribbon seals), this study analyzed samples from 998 seals harvested for subsistence purposes in western and northern Alaska during 2005–2019 for DA and STX. Both toxins were detected in bearded, ringed, and spotted seals, though no clinical signs of acute neurotoxicity were reported in harvested seals. Bearded seals had the highest prevalence of each toxin, followed by ringed seals. Bearded seal stomach content samples from the Bering Sea showed a significant increase in DA prevalence with time (logistic regression, p = .004). These findings are consistent with predicted northward expansion of DA‐producing algae. A comparison of paired samples taken from the stomachs and colons of 15 seals found that colon content consistently had higher concentrations of both toxins. Collectively, these results suggest that ice seals, particularly bearded seals (benthic foraging specialists), are suitable sentinels for monitoring HAB prevalence in the Pacific Arctic and subarctic.

Spatiotemporal transitions in Pseudo-nitzschia species assemblages and domoic acid along the Alaska coast

“…Observations of DA and toxic Pseudo-nitzschia species reported here build upon prior reports of DA in phytoplankton [ 68 ] and higher trophic levels in subpolar and polar regions of the Arctic [ 3 , 7 , 9 , 35 , 69 – 71 ]. These ARISA-based surveys provided sensitive, high-throughput molecular identification of Pseudo-nitzschia species composition in >275 water and sea ice samples collected during summer and fall cruises along the Alaska coast in 2018.…”

Harmful Algal Blooms in the Alaskan Arctic: An Emerging Threat as the Ocean Warms

“…The higher levels of STXs found in clams make them the most toxic vectors identified in the Alaskan Arctic region to date, suggesting that they present a distinct risk to marine mammals and humans. This finding agrees with previous studies showing higher prevalence and concentrations of STXs in clam-feeding walruses and bearded seals compared to other marine wildlife that feed on fish or zooplankton, such as spotted seals, bowhead whales, and seabirds (Lefebvre et al, 2016;Hendrix et al, 2021;Van Hemert et al, 2021a;Lefebvre et al, 2022).…”

“…Although many questions remain about the ecosystem-level impacts of HABs in the Alaskan Arctic, growing evidence indicates the possibility of an emerging wildlife health issue. Recent reports demonstrated increasing prevalence of DA in marine mammals (Hendrix et al, 2021), along with possibly harmful concentrations of STXs in seabirds associated with known mortality events (Van Hemert et al, 2021a). These findings, combined with projections of more frequent and intense STXproducing HABs due to warming ocean conditions in the Arctic (Anderson et al, 2021a), suggest that marine wildlife (and the people who harvest and consume them) may face growing exposure risks.…”

Stratification and summer protist communities in the Arctic influenced coastal systems of Nunavik (Québec, Canada)

“…The marine Arctic has traditionally been considered unfavorable for toxin-producing marine harmful algal blooms (HABs), but numerous potentially harmful algae species have been reported to occur in Canadian Arctic waters, including Hudson Bay (Poulin et al, 2011;Pucḱo et al, 2019;McKenzie et al, 2020;Dhifallah et al, 2021). Toxins produced by many of these algae accumulate in filter-feeding marine bivalves and can be transferred up the food chain with severe health consequences for marine wildlife such as sea birds and marine mammals, in addition to humans (Beltrań et al, 1997;Scholin et al, 2000;Hendrix et al, 2021). Of greatest concern in northern waters are domoic acid and saxitoxin produced respectively by species of Pseudo-nitzschia and Alexandrium that are causative agents of human illness, amnesic and paralytic shellfish poisoning, respectively (Rue and Bruland, 2001).…”

“…Of greatest concern in northern waters are domoic acid and saxitoxin produced respectively by species of Pseudo-nitzschia and Alexandrium that are causative agents of human illness, amnesic and paralytic shellfish poisoning, respectively (Rue and Bruland, 2001). Because HABs are common in temperate and tropical regions, warming Arctic Ocean conditions raise growing concern for the potential expansion of HAB into these regions (Anderson et al, 2021;Hendrix et al, 2021). Moreover, the expected increase of shipping activity associated with the longer open water season, make the coastal HB system particularly vulnerable to the importation of toxic algae from ship ballast and other accidental introductions (Hochheim and Barber, 2014;Andrews et al, 2018).…”