Microbiological and biogeochemical observations in the Greenland Sea at 75° N.

The Arctic and sub-Arctic ecosystems are environmentally sensitive regions, where the impact of global climate change is expected to make marked changes over the next decades and more rapidly than elsewhere. In fact, these regions have been warming more than twice as rapidly as the rest of the world for the past 50 years. The Arctic climate has undergone tremendous change, such as Arctic wetting, reduction of Arctic sea ice thickness and coverage, a decrease of snow cover extent and duration, thawing of permafrost and melting of Greenland ice Sheet. This positive feedback effect is among the main processes responsible for the "Arctic Amplification", which will likely strengthen in the coming years. In this context, the Italian project CASSANDRA is part of the Synoptic Arctic Survey (SAS), in the framework of the Arctic Research Program (PRA), which aims at quantifying the current state of the physical, chemical, biological and biogeochemical systems of a historical subarctic transept at 75°N crossing a cyclonic vortex of the Greenland Sea. CASSANDRA oceanographic cruise was carried out from 29 August to 14 September 2021 onboard the N/R Laura Bassi. Preliminary results will be presented concerning the ecosystem functioning. Water samples were collected along the water column from six stations along the 75°N transect to evaluate the microbial abundance, biomass, activities and metabolism. Interesting results have been determined reflecting the contour characteristics of the large sampled sea area, the possible coastal contribution and the peculiar oceanographic conditions determined along the sampled transect. Comparisons with previous bibliographic data in the same area and seasonal period will be made to verify any modifications of the microbial standing stock and its activity.