Return of warm conditions in the southeastern Bering Sea: Phytoplankton - Fish

• Published in: PLOS ONE
• Main Authors: Duffy-Anderson, Janet T., Stabeno, Phyllis J., Siddon, Elizabeth C., Andrews, Alex G., Cooper, Daniel W., Eisner, Lisa B., Farley, Edward V., Harpold, Colleen E., Heintz, Ron A., Kimmel, David G., Sewall, Fletcher F., Spear, Adam H., Yasumishii, Ellen C.
• Format: Text
• Language: English
• Published: Public Library of Science 2017
• Subjects: Research Article; Bering Sea; Sea ice; Copepods
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5489148/; http://www.ncbi.nlm.nih.gov/pubmed/28658253; https://doi.org/10.1371/journal.pone.0178955

In 2014, the Bering Sea shifted back to warmer ocean temperatures (+2 oC above average), bringing concern for the potential for a new warm stanza and broad biological and ecological cascading effects. In 2015 and 2016 dedicated surveys were executed to study the progression of ocean heating and ecosystem response. We describe ecosystem response to multiple, consecutive years of ocean warming and offer perspective on the broader impacts. Ecosystem changes observed include reduced spring phytoplankton biomass over the southeast Bering Sea shelf relative to the north, lower abundances of large-bodied crustacean zooplankton taxa, and degraded feeding and body condition of age-0 walleye pollock. This suggests poor ecosystem conditions for young pollock production and the risk of significant decline in the number of pollock available to the pollock fishery in 2–3 years. However, we also noted that high quality prey, large copepods and euphausiids, and lower temperatures in the north may have provided a refuge from poor conditions over the southern shelf, potentially buffering the impact of a sequential-year warm stanza on the Bering Sea pollock population. We offer the hypothesis that juvenile (age-0, age-1) pollock may buffer deleterious warm stanza effects by either utilizing high productivity waters associated with the strong, northerly Cold Pool, as a refuge from the warm, low production areas of the southern shelf, or by exploiting alternative prey over the southern shelf. We show that in 2015, the ocean waters influenced by spring sea ice (the Cold Pool) supported robust phytoplankton biomass (spring) comprised of centric diatom chains, a crustacean copepod community comprised of large-bodied taxa (spring, summer), and a large aggregation of midwater fishes, potentially young pollock. In this manner, the Cold Pool may have acted as a trophic refuge in that year. The few age-0 pollock occurring over the southeast shelf consumed high numbers of euphausiids which may have provided a high quality alternate prey. In ...