Collaborative Research: Harmful Algal Blooms in the Pacific Arctic: Modeling the Past and Predicting the Future

Certain species of microscopic phytoplankton produce toxins that can be accumulated by moving up through the food chain to poison animals, such as clams, fish, seals, walruses, whales, and ultimately humans. Recent observations in the Bering and Chukchi seas have identified large populations of Alexandrium catenella, a saxitoxin-producing, harmful species of phytoplankton.

A. catenella germinates from cysts on the seabed as water warms during spring and summer and enters the vegetative stage where they grow and reproduce in the water column, forming a harmful algal bloom (HAB). When the water cools and daylight wanes in autumn the vegetative cells then form dormant cysts, which sink to the seabed. Recent warming of ocean temperatures in the Pacific Arctic, and along the coast of Alaska in particular, presents a distinct threat since A. catenella germination and growth rates increase with increasing temperature.

This project aims to help in understanding the evolving biophysical environment of the Bering and Chukchi seas for decision making related to food security for humans that consume seafood from the region. The project’s key objectives are to identify the major pathways and ‘hotspots’ of A. catenella in the Pacific Arctic. This project will use the Regional Arctic System Model (RASM), which includes ocean, sea ice, atmosphere, and biogeochemistry models, and expand it with a life cycle model of A. catenella.

The expanded model (RASM-HAB) will be used to identify the upstream source regions for the observed cyst accumulation on the Chukchi seabed, which is the largest and most highly concentrated cyst deposition region ever observed in the world ocean. RASM-HAB is uniquely poised to aid understanding of the physical conditions affecting the germination, growth, and advection of HABs due its demonstrated ability to simulate the ocean, sea ice, atmosphere, and biogeochemistry of the Pacific Arctic with high fidelity.

RASM’s domain includes the North Pacific, pan-Arctic, and North Atlantic, including many areas where HAB observations do not exist, such as the western Chukchi Sea, where high concentrations of A. catenella are expected. Model runs covering the previous four decades will provide information on the past interannual variability in HABs and long-term trends.

Finally, 6-month forecasts of physical, biological, and HAB conditions will be completed and assessed for reliability as a proof-of-concept. This work is important because it will improve understanding and potentially prediction of changing germination, growth rates, and movement of HABs in a region of high biological productivity, which provides food resources for Alaskan and greater US populations.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.