Impact of climate forcing and glacial runoff on the coastal, biogeochemical and ecological dynamics of an Arctic fjord (Kongsfjord, Svalbard Islands)

The Arctic region is considered as most sensitive to climate change, with warming occurring considerably faster than the global average. The consequences of this warming determine a cascade of changes in the physical environment, biogeochemical processes, and ecosystem functioning. In Kongsfjorden (Svalbard, Norway), the increase in temperature and precipitation changes in strength, also lead to increased glacial meltwater discharge and river runoff processes within the fjord. Thus, investigating the system's responses to these inputs is crucial in the light of ongoing warming. In this study, two years of sampling in the south coast of the fjord, 2020/2021 and 2021/2022, are analyzed to describe variations concerning particle fluxes and the mesozooplankton and meroplankton community structure, commensurate to the leading environmental processes modifying the fjord system. Results suggest a common seasonal-driven pattern and delineate however inter-annual changes. The year 2021/2022, warmer and affected by more abundant precipitation, experienced a high amount of passive sediment fluxes, coinciding with peaks of air temperature in summer, with particulate matter detected more degraded. Mesozooplankton has lower biodiversity and is dominated by Copepods and Ctenophores while meroplankton is less abundant and dominated by Copepod Nauplii and Euphausiacea larvae. The year 2020/2021 shows lower passive sediment fluxes, with peaks in spring. Mesozooplankton is dominated by Copepods, while high abundances of Zoea stages characterize the meroplankton community. In both years, the particulate matter has a mixed marine-terrestrial origin, although the terrestrial component seems evident in the summer samples. Great abundances of meroplankton in spring are found, rapidly followed by decreasing abundances in summer, describing in both years a disadvantageous season for zooplankton communities with the exception of a few classes of individuals.