title: Allochthonous Carbon--a Major Driver of Bacterioplankton Production in the Subarctic Northern Baltic Sea.
abstract: Heterotrophic bacteria are, in many aquatic systems, reliant on autochthonous organic carbon as their energy source. One exception is low-productive humic lakes, where allochthonous dissolved organic matter (ADOM) is the major driver. We hypothesized that bacterial production (BP) is similarly regulated in subarctic estuaries that receive large amounts of riverine material. BP and potential explanatory factors were measured during May-August 2011 in the subarctic Råne Estuary, northern Sweden. The highest BP was observed in spring, concomitant with the spring river-flush and the lowest rates occurred during summer when primary production (PP) peaked. PLS correlations showed that ∼60% of the BP variation was explained by different ADOM components, measured as humic substances, dissolved organic carbon (DOC) and coloured dissolved organic matter (CDOM). On average, BP was threefold higher than PP. The bioavailability of allochthonous dissolved organic carbon (ADOC) exhibited large spatial and temporal variation; however, the average value was low, ∼2%. Bioassay analysis showed that BP in the near-shore area was potentially carbon limited early in the season, while BP at seaward stations was more commonly limited by nitrogen-phosphorus. Nevertheless, the bioassay indicated that ADOC could contribute significantly to the in situ BP, ∼60%. We conclude that ADOM is a regulator of BP in the studied estuary. Thus, projected climate-induced increases in river discharge suggest that BP will increase in subarctic coastal areas during the coming century.
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-901 87, Umeå, Sweden.|Umeå Marine Sciences Centre, SE-905 71, Hörnefors, Sweden.
authors.forename: D
authors.initials: D
authors.lastname: Figueroa
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-901 87, Umeå, Sweden.|Department of Food and Environmental Sciences, Division of Microbiology and Biotechnology, Viikki Biocenter 1, University of Helsinki, Helsinki, Finland.
authors.forename: O F
authors.initials: OF
authors.lastname: Rowe
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-901 87, Umeå, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Paczkowska
authors.affiliation: Ecology and Evolution in Microbial Model Systems, EEMiS, Department of Biology and Environmental Sciences, Linnaeus University, SE-391 82, Kalmar, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Legrand
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-901 87, Umeå, Sweden. agneta.andersson@umu.se.|Umeå Marine Sciences Centre, SE-905 71, Hörnefors, Sweden. agneta.andersson@umu.se.
authors.forename: A
authors.initials: A
authors.lastname: Andersson
mesh_terms: D001419:Bacteria / Q000254:growth & development* / Q000378:metabolism*; D002244:Carbon / Q000737:chemistry / Q000378:metabolism*; D009659:North Sea; D010933:Plankton / Q000254:growth & development* / Q000378:metabolism*; D012623:Seawater; D013548:Sweden
chemical_list: D002244:Carbon
keywords: Allochthonous organic matter; Bacterioplankton production; Baltic Sea; Carbon utilization; Sub-arctic estuary