Effects of N:P loading ratios on phytoplankton community composition, primary production, and N fixation in a eutrophic lake
2009 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 54, no 2, 331-344 p.Article in journal (Refereed) Published
1. The aim of this study was to assess the effects of different nitrogen (N) to phosphorus (P) loading ratios on phytoplankton community composition and primary production in a naturally eutrophic lake. Furthermore, the sources of N fuelling primary production were estimated using 15N stable isotope tracers.
2. A mesocosm experiment was performed with the same amount of P added to all mesocosms (similar to internal loading rates) but with a range of N additions (0–86 μm N), resulting in a gradient of N : P supply ratios.
3. Low N : P supply ratios resulted in a significant shift in the phytoplankton assemblage to a community dominated by N-fixing cyanobacteria and a supply of atmospheric N2 estimated to be up to 60% of total supply.
4. The N : P loading ratio had no significant effect on primary production, total nitrogen (TN) concentration or particulate N concentration.
5. Our results imply that a reduced N : P ratio of the nutrient load does not necessarily result in a lower TN concentration and downstream N export due to compensation by N-fixing cyanobacteria.
Place, publisher, year, edition, pages
2009. Vol. 54, no 2, 331-344 p.
15N stable isotopes, eutrophication, nitrogen, phosphorus, stoichiometry
IdentifiersURN: urn:nbn:se:uu:diva-111716DOI: 10.1111/j.1365-2427.2008.02118.xISI: 000262470300009OAI: oai:DiVA.org:uu-111716DiVA: diva2:282557