The first major activity of the project took place in August 2017 when I participated in a field campaign to Young Sound. There I set-up a mesocosm experiment to determine the experimental response of adding GrIS melt water to plankton communities from the fjord. Specifically, I was interested in seeing the effects on microbial communities and degradation of the carbon introduced from the GrIS melt water. Initial results indicate an enhanced growth of microbial communities in treatments amended with GrIS melt water. While there was some incorporation of terrestrial carbon, much of the carbon incorporated into microbial biomass was of autochthonous origin. Instead, results suggest that it was actually the formation of flocculated particles from the addition of GrIS meltwater that enhanced bacterial remineralization of organic matter rather than the carbon itself in the melt water.
The second major activity of the project took place in August 2018 when I participated in a field campaign to East Greenland. Along with colleagues I sampled microbial communities to measure primary productivity and bacterial productivity along transects running out fjords. Additionally, I measured stable isotopes of prokaryotic-specific fatty acid biomarkers to determine the contribution of both allochthonous and autochthonous carbon sources to the microbial food web.
Preliminary results indicate gradients of primary production from inner fjord to outer fjord, whereby communities sampled in shelf waters are more productive than those sampled in the inner fjord. Prokaryotic communities in surface water and in the inner fjords have a higher proportion of their production associated to particle attached phases and these communities are more productive overall. Finally, while organic carbon introduced by GrIS melt is highly bioavailable to microbial remineralization, the concentrations of organic carbon in GrIS melt water are an order of magnitude lower than the carbon already available in the fjords, thus organic carbon from GrIS melt water does not appear to subsidize microbial communities in the fjords to a large extent as has previously been suggested in the dominant literature on the topic. Rather, it is likely the particles and subsequent attachment by bacteria rather than subsides of carbon coming in with GrIS melt water are more important to enhance bacterial production in fjords.
Some of the results pertaining to this project have been already been presented in the following peer-reviewed scientific publication and the remaining results will also be exploited in the form of scientific journal publications.
Publication in peer-reviewed open-access journal:
Holding JM, Markager S, Juul-Pedersen T, Paulsen ML, Møller EF, Meire L, Sejr MK (2019) Seasonal and spatial patterns of primary production in a high-latitude fjord affected by Greenland Ice Sheet run-off. Biogeosciences 16:3777–3792.
