Spatial and Interannual Patterns of Epipelagic Summer Mesozooplankton Community Structures in the Western Arctic Ocean in 2016–2020

Abstract

Mesozooplankton play a crucial role as primary or secondary consumers in Arctic ecosystems and are sensitive indicators of environmental changes. This research is the first comprehensive Arctic zooplankton study covering the area ranging from the southern Chukchi Sea (SCS) and the northern Chukchi Sea (NCS) to the East Siberian Sea (ESS). Mesozooplankton samples were collected at 151 stations in the western Arctic Ocean each August from 2016 to 2020. The mesozooplankton abundance of the study area ranged from 9 to 6,172 ind. m−3, and the predominant group was copepods at 7–3,866 ind. m−3, of which Pseudocalanus spp. and Calanus glacialis were the most abundant copepods. In the SCS, small copepods and meroplankton, such as Pseudocalanus spp., Cirripedia larvae, Echinodermata larvae, and Centropages abdominalis were the predominant taxa. Especially in 2019, C. abdominalis dominated over meroplankton when water temperatures were high (maximum 12.5°C; sea surface temperature, SST). In the NCS and ESS, C. glacialis, Pseudocalanus spp., Metridia longa, Oithona similis, Parasagitta elegans, and Calanus hyperboreus were abundant. The distributions and structures of mesozooplankton communities indicated variability over large spatial scales in the western Arctic waters because of variations in multiple factors, such as water temperature, salinity, and sea ice; however, geographical effects cannot be ignored even during alterations in the physical properties. Our results suggest that these variable patterns of mesozooplankton communities fluctuate horizontally from south to north as warming progresses on a regional bathymetric basis, and can be used to infer the fate of mesozooplankton communities in the study area.

Patterns of summer ichthyoplankton distribution, including invasive species, in the Bering and Chukchi Seas

“…Species transportation from the Atlantic and East Siberian regions in this study is consistent with the findings of Wisz et al (2015), who argued that transfers from the Atlantic to the Pacific Ocean would be primarily facilitated through the Northwest Passage. This phenomenon has been confirmed in various taxa (Beaugrand et al, 2002;Perry et al, 2005;Reid et al, 2007;Wisz et al, 2015;Kim et al, 2020, Kim et al, 2022. However, Gadus macrocephalus, another dominant species in the Pacific sub-Arctic regions, has not been observed in this survey although this species is also known as extending their distribution northward (Stevenson and Lauth, 2019;Baker, 2021;Cooper et al, 2023).…”

Hydrographic Feature Variation Caused Pronounced Differences in Planktonic Ciliate Community in the Pacific Arctic Region in the Summer of 2016 and 2019

“…Previous studies have shown that macrozooplankton abundance and biomass increase significantly in warmer waters in recent years compared to historical studies ( Ershova et al, 2015 ; Xu et al, 2018 ; Kim et al, 2022 ). During each August from 2016 to 2020, macrozooplankton abundance was highest in the Bering Strait with higher water temperature ( Kim et al, 2022 ).…”

“…Previous studies have shown that macrozooplankton abundance and biomass increase significantly in warmer waters in recent years compared to historical studies ( Ershova et al, 2015 ; Xu et al, 2018 ; Kim et al, 2022 ). During each August from 2016 to 2020, macrozooplankton abundance was highest in the Bering Strait with higher water temperature ( Kim et al, 2022 ). As important food items of macrozooplankton, we speculate that higher ciliate abundance and biomass in warmer waters of 2019 might be the main reason for higher macrozooplankton abundance.…”

Multi-year variability of summer phytoplankton biomass and size structure in the northern Chukchi and East Siberian Seas, Arctic Ocean: role of light and nutrient availability

“…The August mean nitrate concentration in the upper SCM depth was highest in 2019 (Figure 4B) and is unlikely to be a limiting factor for phytoplankton growth. Grazing pressure at higher trophic levels is likely to be one of the limiting factors for phytoplankton in 2019, as the mesozooplankton abundance was reported to be slightly higher in August 2019 than in August 2018 in the west (Kim et al, 2022). Finally, the mean daily insolation was lowest in 2019 (average 184 mEm -2 d -1 ) in the six-year survey.…”

“…However, the effects of these environmental changes on marine phytoplankton remain poorly understood. Although previous studies have reported data on chlorophyll-a (chl-a) concentrations in the NCESS during specific periods, these data have been used primarily as variables to explain the results in the fields of phytoplankton physiology, marine ecology, and biogeochemistry (Ko et al, 2020;Jung et al, 2021;Kim et al, 2022;Ko et al, 2022). To explore how large-scale climate and local physical forcing affect phytoplankton biomass and communities in the NCESS, we investigated the multi-year (2015)(2016)(2017)(2018)(2019)(2020) distributions of summer (August) chl-a concentrations and size structures using data collected by the Korea-Arctic Ocean Observing System (K-AOOS) program.…”