The northern Bering Sea zooplankton community response to variability in sea ice: evidence from a series of warm and cold periods

Abstract

Recent, unprecedented losses of sea ice have resulted in widespread changes in the northern Bering Sea ecosystem, and this study explores the zooplankton community response. Time-series observations were used to identify zooplankton community changes in the northern (>60°N) Bering Sea (NBS) over a 17 yr period (2002-2018). The overall objective was to determine if the changes in zooplankton populations previously described for the southeastern Bering Sea shelf (<60°N) were also observed in the NBS over alternating warm and cold periods. Particular attention was paid to more recent (2014-2018) years that showed significant losses of sea ice in the NBS (2017/2018) in comparison to a prior warm period (2003-2005) and an intervening cold period (2006-2013). A multivariate framework (redundancy analysis) was used to explore correlations with environmental conditions, and differences in mean abundance across the differing warm and cold periods were tested. The NBS zooplankton community had different responses across each warm and cold period, and the primary driver for the differences in response was sea ice. Redundancy analysis demonstrated that the zooplankton community during the second warm period experienced greater variability compared to the prior warm period. The zooplankton community had higher abundances of small copepods and meroplankton and reduced abundances of Calanus spp. and chaetognaths during the most recent warm period. This suggests that the NBS zooplankton will not be impacted by reduced sea ice when the ice coverage extends south of 60°N, but show community change once a minimum threshold in ice extent and timing of retreat is reached. Shifts in the zooplankton community may have had cascading effects on higher trophic levels that were evident during the latter warm period.

Shifts in the composition and distribution of Pacific Arctic larval fish assemblages in response to rapid ecosystem change

“…Sea ice loss and the wind‐ and current‐driven northward advection of warmer, subarctic waters from the northern Bering Sea expanded the range of boreal species into the Chukchi Sea and constricted spatial distributions of Arctic assemblages, resulting in mixed assemblages in some years and replacement of Arctic taxa in the warmest years. These findings concur with several recent studies, which have likewise found that the warmer seas, increased northward advection, and diminishing sea ice coverage of recent years (particularly since 2017) have perpetuated dramatic and extensive ecological shifts in communities of phytoplankton (Oziel et al, 2020), zooplankton (Huntington et al, 2020; Kimmel et al, 2023; Spear et al, 2019), juvenile and adult fishes (Baker, 2021; Eisner et al, 2020; Marsh et al, 2020; Wildes et al, 2022), and seabirds (Kuletz et al, 2020).…”

Joint species distribution modeling reveals a changing prey landscape for North Pacific right whales on the Bering shelf

“…In addition, movement terms-sea ice extent, cold pool, and wind gusts-were significant to the community. Our results reinforce prior studies that found sea ice and the cold pool significant to the Bering shelf zooplankton community (Coyle & Pinchuk, 2002;Duffy-Anderson et al, 2019;Kimmel et al, 2023; F I G U R E 5 Posterior parameter estimates for zooplankton species abundance to (A) bottom temperature (in degrees Celsius, BT) and surface temperature (in degrees Celsius, ST) in matrix ρ (rho; density-independent growth; Equation 2) and (B) number of days with wind gusts >15 m/s from spring (WGsp; April-May) and fall (WGf; September-October) in matrix β (beta; movement term; Equation 2). Colors correspond to species (red = Calanus glacialis; orange = Neocalanus species; teal = Thysanoessa species; gray = other species).…”

“…Ice has continued to retreat in the Arctic since the years of our study, including an absence of ice in the Bering Sea during the winter of 2017-2018 (Stabeno & Bell, 2019). In the following summer, calanoids and euphausiids had 14% less lipids compared with high-IE years (Duffy-Anderson et al, 2019), and the zooplankton community shifted to smaller, lipid-poor species (Kimmel et al, 2023), suggesting that whales may need to consume more individual prey items in low ice conditions, which could impact foraging effort and targeted prey patch sizes. A 2018 research cruise documented right whales in the southern and northern Bering Sea within a 2-week period of July (Matsuoka et al, 2021), suggesting either a range expansion to find adequate prey, as was proposed by prior tagging work (Zerbini et al, 2015), or a transition to individual foraging strategies.…”

“…The supplemental gjamTime function "wrapper EquilAbund" provided a framework to investigate whether inclusion of movement (i.e., migration/emigration) into the model framework would impact the steadystate (i.e., equilibrium) abundance of C. glacialis over a gradient in bottom water temperature. We chose bottom water temperature because of its significance for our model and prior studies on C. glacialis from the region (e.g., Coyle et al, 2008Coyle et al, , 2011Eisner et al, 2014;Hunt Jr. et al, 2011Kimmel et al, 2023). We hypothesized the inclusion of movement would impact steady-state abundance by allowing both C. glacialis to move out of the study region and advection of potential competitor outer-shelf large-bodied species (Neocalanus and Thysanoessa) into the study region under warm ocean conditions (Campbell et al, 2016;Hunt Jr. et al, 2016).…”

Response of the copepod community to interannual differences in sea-ice cover and water masses in the northern Barents Sea

“…In the Bering Sea, largesized Calanus spp. were found to be more abundant during cold periods with extensive sea-ice cover (Coyle and Pinchuk, 2002;Hunt et al, 2011;Stabeno et al, 2012;Eisner et al, 2014;Kimmel et al, 2018, Kimmel et al, 2023, while small copepods (e.g. Oithona spp.…”