Iron Constraints on Planktonic Primary Production in Oligotrophic Lakes

We show that P was the nutrient that stimulated phytoplankton primary production most strongly in seven out of nine bioassay experiments with natural lake water from oligotrophic clearwater lakes

Tobias Vrede; Lars J. Tranvik


Scholarcy highlights

  • In pelagic ecosystems, primary production of phytoplankton is constrained by light and nutrients, and much attention has been paid to limitation by phosphorus and nitrogen
  • The nine lakes sampled for bioassay experiments are oligotrophic clearwater lakes with total phosphorus concentrations of 0.04–0.20 lM P, and dissolved organic carbon1
  • Phytoplankton primary production was primarily limited by P in most lakes, but concurrent limitation of phytoplankton primary production by P, Fe and N occurred frequently in these oligotrophic clearwater lakes
  • An increased load of P to the lakes would increase the net primary production, but the phytoplankton community is expected to become limited by Fe and/or N
  • Fe addition had the strongest effect on primary production in the lake with the lowest TP and DOC concentrations, and the results from the ANCOVA show that the effect of adding Fe increased with decreasing TP and DOC
  • Different responses in different taxa may allow the phytoplankton community to be locally adapted to the prevailing situation, where scarcity of a particular nutrient is buffered at the community level by selection for
  • Nutrient limitation of primary production in lakes has to a large extent been studied in regions with significant anthropogenic influence, and in relatively eutrophic waters

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