Origin and Fate of Harmful Algal Blooms in the Warming Chukchi Sea

Abstract

The Pacific sector of the Arctic Ocean is warming, in particular the shallow Chukchi Sea. As a result, it is anticipated that many organisms may migrate northward or become more abundant as air and ocean temperatures continue to warm. However, few pose such significant threats to human and ecosystem health as harmful algal bloom (HAB) species. Data collected over the past decade clearly indicate that multiple toxic HAB species are present in the Arctic food web at dangerous levels, and it is very likely that this problem will persist and perhaps worsen in the future. HABs occur in the Chukchi Sea and we know that the potent neurotoxins they produce can affect marine mammals, seabirds, and other resources critical to subsistence harvesters. At the same time, little is known about the present and future risk from toxic algae to humans in the Pacific Arctic region. This study will investigate the current distribution of highly toxic HAB species at high resolution over large spatial scales within the Alaskan Arctic and along its transport pathways, and will provide estimates of areas at high risk of toxicity now and in a warming future. The investigators will disseminate results via brochures, public lectures, and radio interviews in Native communities, as well as through discussions with local scientists and managers. A PolarTREC teacher from Alaska will participate in research activities and will help introduce HAB science to K-12 classrooms.

The hypothesis underlying this project is that harmful algal bloom species (HABs) in Alaskan Arctic waters are not only advected from the south through Bering Strait but are now originating locally on the Chukchi shelf due to warming temperatures, circulation dynamics, and water mass structure that influence bloom magnitude, duration, toxicity, and recurrence. This will be addressed through a joint physical-biological field and laboratory program to study the relationship between HAB species distribution/dynamics and the physical environment of the Chukchi Sea region. The distribution of HAB species on the Chukchi shelf will be mapped in relation to hydrography and circulation, including a comprehensive survey of the Alaskan Coastal Current which transports the warmest water in the Chukchi Sea. A range of molecular and physiological tools will be used to investigate the origin, connectivity, and fate of HAB populations in the region in the context of large-scale wind forcing and partitioning of water masses flowing through Bering Strait and the Chukchi Sea. Cyst and isotope profiling will establish a historical record of blooms along the major transport pathways to the western Arctic. Finally, conceptual models of the origin, transport, and fate of HABs in the Chukchi Sea region will elucidate linkages to the flow pathways, dynamics, and characteristics of the different water masses.

Logistics Summary

This project will study the relationship between harmful algal blooms and the physical environment of the Chukchi Sea. The researchers believe that these algal blooms have historically come up from the Bering Sea, but increasingly they originate locally in the Chukchi shelf due to warming temperatures, circulation dynamics, and water mass structure that influence bloom magnitude, duration, toxicity, and recurrence. Fieldwork will be conducted from the R/V Norseman II and researchers on the cruise will focus on harmful algal blooms between the northern Bering Sea and western Beaufort Sea. This fieldwork was originally scheduled for 2020 and then 2021 but was delayed due to COVID-19 restrictions. During July/August of 2022, 16 researchers and a PolarTREC teacher will embark on a 28-day cruise (Leg One) aboard the R/V Norseman II out of Nome, sampling locations comprising nine transects from the northern Bering Sea to the western Beaufort Sea. A second cruise will take place in August/September for 21 days (Leg Two), repeating the same route as Leg One, to the extent possible. Leg One will focus primarily on the Harmful Algal Blooms (HABs) and Leg Two will focus on the Biogeochemical (BGC) survey (see Appendix A). Researchers will take samples from approximately 250 stations, consisting of CTDs, water sampling, plankton tows, grab sampling, multi-cores, and gravity cores, between 62 and 73 degrees of Latitude. Additionally, three researchers will conduct work aboard the R/V Norseman II during transit between Homer and Nome before starting Leg One. PolarTREC teacher Rebecca Siegel (1918637RS) will join the field team for Leg One aboard the R/V Norseman II. During August/September of 2024, three researchers will visit the Nome/St. Lawrence Island region to communicate their recent findings and implications from the 2022 cruise, discuss potential HAB impacts to food safety and security in local communities, and learn about the knowledge and history of HABs in the area.

Battelle ARO will provide R/V Norseman II charter, transportation in Nome, cargo support in Nome, float coats, air support and lodging for outreach in Nome and surrounding areas, and a remote community observer based in Utqiagvik. All other logistics will be arranged and paid for by the PI from the research grant.