Among the organisms that spread into and flourish in Arctic waters with rising temperatures and sea ice loss are toxic algae, a group of harmful algal bloom species that produce potent biotoxins. Alexandrium catenella, a cyst-forming dinoflagellate that causes paralytic shellfish poisoning worldwide, has been a significant threat to human health in southeastern Alaska for centuries. It is known to be transported into Arctic regions in waters transiting northward through the Bering Strait, yet there is little recognition of this organism as a human health concern north of the Strait. Here, we describe an exceptionally large A. catenella benthic cyst bed and hydrographic conditions across the Chukchi Sea that support germination and development of recurrent, locally originating and self-seeding blooms. Two prominent cyst accumulation zones result from deposition promoted by weak circulation. Cyst concentrations are among the highest reported globally for this species, and the cyst bed is at least 6× larger in area than any other. These extraordinary accumulations are attributed to repeated inputs from advected southern blooms and to localized cyst formation and deposition. Over the past two decades, warming has likely increased the magnitude of the germination flux twofold and advanced the timing of cell inoculation into the euphotic zone by 20 d. Conditions are also now favorable for bloom development in surface waters. The region is poised to support annually recurrent A. catenella blooms that are massive in scale, posing a significant and worrisome threat to public and ecosystem health in Alaskan Arctic communities where economies are subsistence based.
The Pacific Arctic region is characterized by seasonal sea‐ice, the spatial extent and duration of which varies considerably. In this region, diatoms are the dominant phytoplankton group during spring and summer. To facilitate survival during periods that are less favorable for growth, many diatom species produce resting stages that settle to the seafloor and can serve as a potential inoculum for subsequent blooms. Since diatom assemblage composition is closely related to sea‐ice dynamics, detailed studies of biophysical interactions are fundamental to understanding the lower trophic levels of ecosystems in the Pacific Arctic. One way to explore this relationship is by comparing the distribution and abundance of diatom resting stages with patterns of sea‐ice coverage. In this study, we quantified viable diatom resting stages in sediments collected during summer and autumn 2018 and explored their relationship to sea‐ice extent during the previous winter and spring. Diatom assemblages were clearly dependent on the variable timing of the sea‐ice retreat and accompanying light conditions. In areas where sea‐ice retreated earlier, open‐water species such as Chaetoceros spp. and Thalassiosira spp. were abundant. In contrast, proportional abundances of Attheya spp. and pennate diatom species that are commonly observed in sea‐ice were higher in areas where diatoms experienced higher light levels and longer day length in/under the sea‐ice. This study demonstrates that sea‐ice dynamics are an important determinant of diatom species composition and distribution in the Pacific Arctic region.
Harmful algal blooms (HABs) present an emerging threat to human and ecosystem health in the Alaskan Arctic. Two HAB toxins are of concern in the region: saxitoxins (STXs), a family of compounds produced by the dinoflagellate Alexandrium catenella, and domoic acid (DA), produced by multiple species in the diatom genus Pseudo-nitzschia. These potent neurotoxins cause paralytic and amnesic shellfish poisoning, respectively, in humans, and can accumulate in marine organisms through food web transfer, causing illness and mortality among a suite of wildlife species. With pronounced warming in the Arctic, along with enhanced transport of cells from southern waters, there is significant potential for more frequent and larger HABs of both types. STXs and DA have been detected in the tissues of a range of marine organisms in the region, many of which are important food resources for local residents. The unique nature of the Alaskan Arctic, including difficult logistical access, lack of response infrastructure, and reliance of coastal populations on the noncommercial acquisition of marine resources for nutritional, cultural, and economic well-being, poses urgent and significant challenges as this region warms and the potential for impacts from HABs expands.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.