Cold Regime Interannual Variability of Primary and Secondary Producer Community Composition in the Southeastern Bering Sea

Abstract

Variability of hydrographic conditions and primary and secondary productivity between cold and warm climatic regimes in the Bering Sea has been the subject of much study in recent years, while interannual variability within a single regime and across multiple trophic levels has been less well-documented. Measurements from an instrumented mooring on the southeastern shelf of the Bering Sea were analyzed for the spring-to-summer transitions within the cold regime years of 2009–2012 to investigate the interannual variability of hydrographic conditions, primary producer biomass, and acoustically-derived secondary producer and consumer abundance and community structure. Hydrographic conditions in 2012 were significantly different than in 2009, 2010, and 2011, driven largely by increased ice extent and thickness, later ice retreat, and earlier stratification of the water column. Primary producer biomass was more tightly coupled to hydrographic conditions in 2012 than in 2009 or 2011, and shallow and mid-column phytoplankton blooms tended to occur independent of one another. There was a high degree of variability in the relationships between different classes of secondary producers and hydrographic conditions, evidence of significant intra-consumer interactions, and trade-offs between different consumer size classes in each year. Phytoplankton blooms stimulated different populations of secondary producers in each year, and summer consumer populations appeared to determine dominant populations in the subsequent spring. Overall, primary producers and secondary producers were more tightly coupled to each other and to hydrographic conditions in the coldest year compared to the warmer years. The highly variable nature of the interactions between the atmospherically-driven hydrographic environment, primary and secondary producers, and within food webs underscores the need to revisit how climatic regimes within the Bering Sea are defined and predicted to function given changing climate scenarios.

Copepod dynamics across warm and cold periods in the eastern Bering Sea: Implications for walleye pollock (Gadus chalcogrammus) and the Oscillating Control Hypothesis

“…The mechanism that has been proposed to explain these observed patterns focuses on the atmosphere‐ice‐ocean dynamics that influence water temperature and phytoplankton production (Napp, Kendall, & Schumacher, ; Sigler et al., ). Cold years on the southeastern Bering Sea shelf have significant winter sea‐ice extent, colder water temperatures, and an ice‐associated spring algal bloom (Hunt et al., ; Sigler, Stabeno, Eisner, Napp, & Mueter, ; Stabeno, Bond, Kachel, Salo, & Schumacher, ; Stabeno, Schumacher, Davis, & Napp, ), although considerable variability within cold years is observed (Stauffer, Miksis‐Olds, & Goes, ). Warm years are ice‐free, have warmer water temperatures, and an open‐water spring bloom as the water column stratifies (Hunt et al., ; Sambroto et al.,; Sigler et al., ; Stabeno et al., ).…”

“…Warm years are ice‐free, have warmer water temperatures, and an open‐water spring bloom as the water column stratifies (Hunt et al., ; Sambroto et al.,; Sigler et al., ; Stabeno et al., ). The combined effects of primary production and temperature have been hypothesized to drive the observed differences in the zooplankton community (Banas et al., ; Coyle et al., ; Hunt et al., ; Sigler et al., ; Stauffer et al., ).…”

“…The combined effects of primary production and temperature have been hypothesized to drive the observed differences in the zooplankton community (Banas et al, 2016;Coyle et al, 2011;Hunt et al, 2011;Sigler et al, 2014;Stauffer et al, 2015).…”

Acoustic documentation of temperate odontocetes in the Bering and Chukchi Seas

“…() study concluded with records from 2012 when a cold climatic regime in the Bering Sea, which started in 2009, shifted to a warm climatic regime (Stauffer et al . ). These four cold climate years from 2009 to 2012, and particularly 2012, saw more expansive and thicker ice that retreated later in the season, stratifying the water column earlier and more tightly coupling the biomass of primary production with hydrographic conditions (Stauffer et al .…”

“…These four cold climate years from 2009 to 2012, and particularly 2012, saw more expansive and thicker ice that retreated later in the season, stratifying the water column earlier and more tightly coupling the biomass of primary production with hydrographic conditions (Stauffer et al . ). During cold climate years, the Oscillating Control Hypothesis (OCH) states that fisheries are controlled by bottom‐up mechanisms and biomass is transported to benthic communities instead of pelagic fishery populations (Hunt et al .…”