Phytoplankton growth and microzooplankton grazing along a sub-Arctic fjord (Godthåbsfjord, west Greenland)

• Published in: Marine Ecology Progress Series
• Main Authors: Calbet, Albert, Riisgaard, Karen, Saiz, Enric, Zamora, Sara, Stedmon, C., Gissel Nielsen, Torkel
• Format: Article in Journal/Newspaper
• Language: English
• Published: Inter Research 2011
• Subjects: West Greenland coast; Sub-Arctic fjord; Plankton community structure; Microzooplankton; Grazing; Arctic; Fyllas Bank; Greenland; glacier; Godthåbsfjord; Phytoplankton; Subarctic
• Online Access: https://doi.org/10.3354/meps09343

12 pages, 7 figures, 4 tables We evaluated the role of microzooplankton (sensu latto, grazers <500 µm) in determining the fate of phytoplankton production (PP) along a glacier-to-open sea transect in the Greenland subarctic fjord, Godthåbfjord. Based on the distribution of size fractionated chlorophyll a (chl a) concentrations we established 4 zones: (1) Fyllas Bank, characterized by deep chl a maxima (ca. 30 to 40 m) consisting of large cells, (2) the mouth and main branch of the fjord, where phytoplankton was relatively homogeneously distributed in the upper 30 m layer, (3) inner waters influenced by glacial melt water and upwelling, with high chl a concentrations (up to 12 µg l−1) in the >10 µm fraction within a narrow (2 m) subsurface layer, and (4) the Kapisigdlit branch of the fjord, ice-free, and characterized with a thick and deep chl a maximum layer. Overall, microzooplankton grazing impact on primary production was variable and seldom significant in the Fyllas Bank and mouth of the fjord, quite intensive (up to >100% potential PP consumed daily) in the middle part of the main and Kapisigdlit branches of the fjord, and rather low and unable to control the fast growing phytoplankton population inhabiting the nutrient rich waters in the upwelling area in the vicinity of the glacier. Most of the grazing impact was on the <10 µm phytoplankton fraction, and the major grazers of the system seem to be >20 µm microzooplankton, as deducted from additional dilution experiments removing this size fraction. Overall, little or no export of phytoplankton out of the fjord to the Fyllas Bank can be determined from our data This research was funded by the project BOFYGO (from the board of the Danish Centre for Marine Research, DCH) and projects Oithogreen (CTM2010-10036-E) and PROTOS (CTM2009-08783) (funded by the Ministry of Science and Innovation) assigned to T.G.N., E.S. and A.C., respectively Peer reviewed