Marine Plankton during the Polar Night: Environmental Predictors of Spatial Variability

Abstract

We studied the spatial patterns of the planktonic ecosystems at two Arctic sites strongly affected by Atlantic Inflow (FS, the Fram Strait; and BS, the Barents Sea). A high degree of similarity in the bacterial abundance (mean: 3.1 × 105 cells mL−1 in FS vs. 3.5 × 105 cells mL−1 in BS) was found, while other plankton characteristics were different. Bacterial biomass reached a maximum in BS (3.2–7.9 mgC m−3), while viral abundances tended to be higher in FS (2.0–5.7 × 106 particles mL−1). Larger bacterial cells were found in BS, suggesting the presence of different bacterial populations at both locations. The virus-to-bacteria ratio was significantly higher in FS than in BS (13.5 vs. 4.7). Chlorophyll a concentration was extremely low (<0.25 mg m−3). The highest zooplankton abundance was in the surface layer (919 individuals m−3 in FS vs. 602 ind. m−3 in BS). Zooplankton biomass strongly varied (1–39 mgC m−3), with the maximum in BS. High proportions of boreal taxa in the total zooplankton abundance indicate the Atlantification of pelagic ecosystems in the Arctic. Plankton indicators are correlated with temperature, salinity, and sampling depth. Strong intercorrelations were found between major plankton groups, suggesting tight links in the studied plankton ecosystems.

The global distribution and climate resilience of marine heterotrophic prokaryotes

“…Therefore, when calculating total prokaryotic biomass, we are assuming that the relationship between cell-specific carbon and temperature is similar across both depth and latitude in colder waters. Cell biovolumes in polar waters might not differ substantially from our Malaspina dataset 31 , and latitudinal increases in cell-specific carbon biomass have previously been reported 32 , which would support our assumption here. Changes in prokaryote prevalence in surface waters were relatively small compared to the magnitude of variability in environmental conditions.…”

Multi-year mesozooplankton flux trends in Kongsfjorden, Svalbard

“…Ocean currents have been shown to affect the number of zooplankton moving through the Fram Strait, and found that copepods rich in carbon, like C. finmarchicus, were abundant (Basedow et al 2018). Even in winter, copepods, especially Calanus species, were still dominant in the waters around Svalbard (Dvoretsky and Dvoretsky 2020;Dvoretsky et al 2023). The influence of AW on zooplankton in Kongsfjorden varies depending on local ocean conditions, as recent research has shown (Gluchowska et al ).…”