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Molecular size of riverine dissolved organic matter influences coastal phytoplankton communities

  • Tony Fagerberg
  • Therese Jephson
  • Per Carlsson
Publishing year: 2010
Language: English
Pages: 17-25
Publication/Series: Marine Ecology - Progress Series
Volume: 409
Document type: Journal article
Publisher: Inter-Research

Abstract english

Dissolved organic matter (DOM) concentrations in many northern European freshwater systems have been increasing during the past decades. DOM affects the marine plankton community where rivers discharge into the sea. Large DOM molecules have been suggested to be more available to aquatic plankton than smaller ones due to their more recent origin in the degradation process. In this study, we investigated the effect of riverine DOM molecular size on coastal plankton with the hypothesis that nitrogen associated with large molecules stimulates the plankton more than nitrogen in smaller molecules. Three size fractions of riverine DOM were isolated with tangential ultrafiltration and introduced at similar nitrogen concentrations to mesocosms with a natural coastal marine plankton community under nitrogen limiting conditions. The results show that growth of bacteria and dinoflagellates, but not diatoms, was stimulated by addition of large DOM molecules. Even though organic nitrogen concentrations tended to decrease more in large DOM treatments compared to smaller DOM treatments, no significant differences were detected. However, proteolytic enzyme activities were elevated in treatments with the largest DOM molecules, suggesting that more organic nitrogen was utilized in this treatment. We suggest that input of larger river DOM molecules to nitrogen limited coastal systems may influence the composition of the coastal phytoplankton community in favour of dinoflagellates.


  • Ecology
  • Molecular size
  • DON
  • River
  • Dissolved organic matter
  • DOM
  • Marine
  • phytoplankton


  • ISSN: 1616-1599
Per Carlsson
E-mail: per [dot] carlsson [at] biol [dot] lu [dot] se

Senior lecturer

Division aquatic ecology

+46 46 222 84 35



Senior lecturer

Aquatic Ecology


Research group

Aquatic Ecology


Marine Pelagic Projects

Doctoral students and postdocs

PhD student, main supervisor

Johanna Stedt