Small meter-scale (1–10 m) spatial variability in snow depth, sea ice properties, ice algal biomass and photobiology

Abstract

Sea ice physical, biological, and chemical properties vary across a wide range of spatial scales, from meters to hundreds or thousands of meters. This spatial variability is commonly attributed to differ-ences in air and ice temperatures, light availability, snow cover thickness, grazing by protozoa, and ocean currents. In situ time series experiments on sea ice are widely used to examine temporal changes in ice algal biomass and photo-physiology in response to specific drivers and light particu-larly. A key assumption in such studies is that observed temporal changes reflect changes in the driving factors rather than spatial variability within the experimental area. Here, we investigate the spatial variability of sea ice physical, chemical properties, ice algal biomass, and algal photobiology at the small spatial scale commonly applied in in situ experiments. Measurements were conducted at 16 sites within a 6 × 6 m plot on land-fast first-year sea ice in Malene Bight, SW Greenland. Sea ice temperature, bulk salinity, Chlorophyll a concentration, and photobiological parameters derived from Pulse Amplitude Modulated (PAM) fluorometry were assessed on the bottom 5 cm of sea ice along with snow depth and sea ice thickness. No statistically significant spatial variability was de-tected for any of the measured parameters, but significant negative correlations were observed be-tween snow depth and maximum quantum yield (ΦPSII_max), and between snow depth and ice thick-ness. The ice algal community was dominated by flagellates (50.4%) and diatoms (48.5%) based on 3 individual samples from the sampling site. These results support the assumption of spatial homo-geneity at meter scales commonly applied in in situ time series studies of sea ice processes, while highlighting snow depth as a key modulator of ice thickness and algal photo-physiology.

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