FY 2026

High-resolution primary and net community productivity estimates in the southeast Bering Sea from moored observations

Cynar, H., L.W. Juranek, N.A. Pelland, J.M. Nielsen, C.W. Mordy, L.B. Eisner, S.W. Bell, N.M. Monacci, P.J. Stabeno, H. Tabisola, and S.E. Stalin

J. Geophys. Res., 130(11), e2024JC022013, doi: 10.1029/2024JC022013, View article at AGU/Wiley (external link) (2025)

The Bering Sea is a highly productive subarctic ecosystem with some of the most valuable commercial fisheries in the United States. This seasonally ice-covered sea has been rapidly changing due to ocean warming with impacts to the ecosystem structure and fisheries. The long-term effects of these shifts on primary producers, however, are still unknown. Continuous monitoring of primary productivity in the Bering Sea is critical, yet observations that capture the ephemeral nature of plankton are challenging to sustain. To address this gap, high temporal resolution primary productivity rates were quantified at a mooring site (M2) in the southeastern Bering Sea in 2021. From a suite of sensors at M2 (fluorescence, dissolved oxygen, temperature, and total dissolved gas pressure), we calculated gross primary productivity (GPP), net primary productivity (NPP), and net community productivity (NCP), the latter based on net biological oxygen saturation using dissolved oxygen/nitrogen (O2/N2) ratios. These estimates elucidate weekly patterns from the spring bloom through fall, when the water column becomes well-mixed. In 2021, we observed average productivity during the spring bloom, yet wind patterns and mixing dynamics during the spring contributed to low productivity during summer and fall. The 2021 productivity metrics (GPP, NPP, and NCP) were compared across the growing season and contrasted with seasonal productivity estimates at M2 in previous years with consideration given to variability of ice conditions (warm/cold years) and wind stress.

Plain Language Summary. The southeast Bering Sea is an important ecosystem that supports substantial economically valuable fisheries. With warming ocean temperatures and less sea ice in this region, the ecosystem is changing with effects on primary producers such as phytoplankton at the base of the food web. Continued monitoring is needed to detect and understand these physical changes and cascading ecosystem effects going forward. At M2, a long-studied site in this region, we deployed instruments in the surface ocean from May 2021 until February 2022. Primary productivity (phytoplankton growth) was estimated from measurements made at M2 from spring though early fall 2021, and a method based on tracer gases (oxygen and nitrogen) to estimate net community productivity was used for the first time at this location. This method provided information on the balance between phytoplankton growth and consumption of phytoplankton biomass, and how this changed from spring through summer and into fall. In comparing these results to net community and primary productivity estimates from prior years at M2, we observed that wind patterns were partially responsible for both the quantity and seasonal patterns of productivity. This technique could be used more broadly to expand upon net community productivity measurements especially in remote areas.