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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14796

Impacts of climate change on Bering Sea copepod phenology and reproductive strategy

Genoa H. Sullaway*, Curry Cunningham, David G. Kimmel, Jens M. Nielsen, Darren Pilcher, Alexei I. Pinchuk, Phyllis J. Stabeno

*Corresponding author:

ABSTRACT: Rapid environmental changes in high latitude marine ecosystems have led to warmer ocean temperatures as well as shifts in zooplankton abundance, community composition, and life history. Variation in zooplankton abundance and phenology, here defined as inferred changes in egg production timing (reproductive phenology) and differences in developmental rates that result in changes to observed life stage composition, are tightly coupled to climate processes. Further, zooplankton represent a critical trophic foundation for commercially important fish communities. To better understand how zooplankton phenology has responded to recent climate perturbations, we examined changes in life stage composition for 2 copepod species groups in the Eastern Bering Sea—Calanus spp. (Calanus glacialis and C. marshallae) and Neocalanus spp. (Neocalanus plumchrus and N. flemingeri)—across a 20 yr timeseries, using generalized additive models. We found that annual shifts in Calanus spp. and Neocalanus spp. phenology are mediated by temperature and spring southwesterly wind frequency. Specifically, warmer temperatures and reduced spring SW wind frequency were associated with younger copepod life stages, which suggests an earlier spring phenology. We also tested if an extended zooplankton growing season has enabled production of a second Calanus spp. generation. We found evidence of earlier spring Calanus spp. reproduction and observed high proportions of younger life stages in fall, both suggesting a second generation of Calanus spp. in some warm years. Collectively, these results suggest fundamental climate-linked changes to copepod phenology and reproduction, which impact population dynamics of copepods and could consequently disrupt elements of the Bering Sea trophic structure that rely upon these energetically dense species.