Dark plumes of glacial meltwater affect vertical distribution of zooplankton in the Arctic

Abstract

In polar regions, the release of glacial meltwater resulting in turbid plumes is expected to transform coastal waters with numerous consequences on the marine ecosystem. This study aimed to determine the influence of turbidity regimes on the vertical distribution of copepods together with their potential food (chlorophyll a fluorescence) and non-visual predators (gelatinous zooplankton). Hydrography, turbidity, suspended particulate matter and chlorophyll a were studied in July and August 2019 in West Spitsbergen waters (European Arctic). Fine-scale vertical distribution patterns of zooplankton were assessed by an optical counter (LOPC) and underwater camera (UVP) and verified by plankton nets. In waters with the shallow impact of dark plumes, Calanus spp. and gelatinous zooplankton were concentrated in the upper water layers, whereas in areas with a thick turbid layer, they were distributed evenly in the water column. However, chlorophyll a peaks were found to be restricted to the surface in the turbid waters and there were subsurface maxima in the shallow turbidity regime. Regardless of the region, the turbidity regime was a significant factor shaping the vertical distribution of Calanus spp. We speculate that similar trends might be observed in other rapidly emerging turbid ecosystems and urge that future plankton research should also include relatively simple turbidity measurements.

The estimates of carbon sequestration potential in an expanding Arctic fjord affected by dark plumes of glacial meltwater (Hornsund, Svalbard)

“…Observational data and previous modelling studies showed that the continuing retreat of marine-terminating glaciers will negatively affect planktic and benthic communities, especially in enclosed shallow bays such as Brepollen (Fig. 7a) (Neder et al, 2022;Szeligowska et al, 2022Szeligowska et al, , 2021Torsvik et al, 2019). Indeed, we observed decreases in phytoplankton, zooplankton, and macrobenthos biomass, and delays in their peak occurrence close to the glacial fronts (by around 10-14 days as compared to the noSPM scenario, Fig.…”

Productivity of Spitsbergen fjords ecosystems in summer—Spatial changes of in situ primary production in Kongsfjorden and Hornsund in the period 1994–2019

“…Chlorophyll a algorithms that utilize satellite data tend to overestimate chlorophyll content, primarily due to the presence of colored dissolved organic matter (CDOM) in the water, mineral suspensions, and the influences of land and icebergs, which can affect the satellite signal. Recent studies indicate that in Svalbard fjords, there is an observed increase in the seasonal release of glacial runoff, accompanied by a positive trend in the darkening of seawater in this region (Konik et al., 2021 ; Szeligowska et al., 2022 ). The correlation between runoff and suspended sediment load is complex, with significant variability observed at the catchment level.…”