Coastal fjord systems around Greenland sustain a high marine productivity and important fisheries, as such fulfill an important ecological and economical function. These fjords are fed by marine-terminating (MTG) and land-terminating glaciers (LTG). Global warming significantly impacts these systems through the accelerated melting of the Greenland ice sheet. This does not only increase total freshwater input into the fjords, but also leads to an accelerated retreat of MTGs, causing them to become LTGs in the near future. Previous studies shown that, in contrast to fjords with LTGs, summer upwelling of deep, nutrient-rich water induced by MTGs significantly increases productivity in their vicinity. It is hypothesized that this phenomenon causes fundamental differences in the structure and function of the pelagic compartment in both fjords types. We will present the results of two sampling campaigns (summer 2021 and spring 2022) carried out in the two main fjord systems near Nuuk, namely Nuup Kangerlua, dominated by MTG, and Ameralik, impacted by a LTG. Analyses of microbial community structure (DNA metabarcoding, Imaging Flow Cytometry, FlowCam, pigments), primary production, marine gel production (TEP), microzooplankton grazing and community respiration rates were carried out to assess differences in dynamics and functioning in the pelagic microbial compartment of the two fjords. Our results may help formulate hypotheses on what the future implications of accelerating melting of the Greenland ice sheet will be on food web structure and the carbon cycle.

Primary Presenter: Marta Mikhno, Gent University (marta.mikhno@ugent.be)

Authors:

Marta Mikhno,   ()

Renaat Dasseville,   ()

Lorenz Meire,   ()

Koen Sabbe,   ()