Spatial patterns in chlorophyll a concentration during the winter–spring periods in the Barents Sea

Abstract

Climatic fluctuations have been documented to strongly affect Arctic marine ecosystems. Plankton assemblages serve as the most sensitive indicators of such environmental forcing. We conducted a study to investigate the spatial variability of chlorophyll a (Chl-a) concentration during two pre-bloom periods (March–April 2021 and February–March 2022) in relation to the distribution of different water masses and associated properties. The upper 50 m layer of the water column was homogeneous and stable, characterized by high nutrient concentrations. Our mapping of the Barents Sea based on Chl-a concentrations revealed low estimates during the winter period. In contrast, two distinct Chl-a peaks were observed in the spring. The first region with high Chl-a concentrations was identified in Murmansk Coastal Water and Atlantic Water (0.7–1.4 mg m⁻³), reflecting the positive impact of the frontal zone between these interacting water masses. The second region with elevated Chl-a concentrations (0.9–1.1 mg m⁻³) was located in Kolguev-Pechora Water near the southeastern ice edge. Cold water regions (Barents Sea Water, Arctic Water, Novaya Zemlya Coastal Water) exhibited low spring Chl-a concentrations (0.03–0.3 mg m⁻³). Generalized additive models identified hydrological variables (temperature and salinity), dissolved oxygen content, and nutrient concentrations (nitrite, nitrate, phosphate) as significant predictors explaining a substantial portion of the Chl-a variability.