Water nutrient stoichiometry modifies the nutritional quality of phytoplankton and somatic growth of crustacean mesozooplankton
2013 (English)In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 489, 93-+ p.Article in journal (Refereed) Published
Here, we investigated how changes in water nutrient stoichiometry may change the nutritional quality of phytoplankton for mesozooplankton. For 6 d, we added nutrients to nine 1300 l mesocosms with natural summer phytoplankton from the Baltic Sea to create communities that were N-limited (P-treatment), Si-limited (PN-treatment) and not limited by nutients (PNSi-treatment). With the addition of P, no major changes occurred in phytoplankton biomass or species composition with time. With the addition of P and N, with or without excess of Si, C: N ratios approached the Redfield ratio, biomass increased and diatoms and dinoflagellates became dominant. Analysis of the 18S rRNA gene showed that the availability and diversity of phytoplankton other than diatoms and dinoflagellates, like prasinophytes or heterotrophic flagellates and ciliates, were not affected by the nutrient treatments. We then tested how the modified phytoplankton communities affected somatic growth in a natural mesozooplankton community dominated by the copepod genus Acartia. After 6 d of grazing, the zooplankton more than doubled their C content per individual when grazing on the Si-limited phytoplankton (PN-treatment) while total community biomass was maintained. In the other 2 treatments, the C content per individual remained the same and total community biomass decreased by ca. 60%, which suggests that the zooplankton was not optimally fed. Thus, a phytoplankton community with stoichiometry close to the Redfield ratio provided the best nutritional quality for the zooplankton, but not when the diatoms were Si saturated. This study shows that nutrient stoichiometry in the seawater can affect zooplankton growth by modification of the phytoplankton community. It also shows that the food quality of phytoplankton does not depend only on the taxonomic composition, but also on the nutrient stoichiometry.
Place, publisher, year, edition, pages
2013. Vol. 489, 93-+ p.
Eutrophication, Phytoplankton, Grazing, Mesozooplankton, Mesocosm experiment, Pigment composition, 18S rRNA gene
Ecology Oceanography, Hydrology, Water Resources
IdentifiersURN: urn:nbn:se:su:diva-94197DOI: 10.3354/meps10438ISI: 000323941000008OAI: oai:DiVA.org:su-94197DiVA: diva2:652410
Swedish Research Council for Environment, Agricultural Science and Spatial Planning; Knut and Alice Wallenberg Foundation; Norsk Hydro Research Foundation; Ebba and Sven Schwarz' Foundation 2013-09-302013-09-302013-09-30Bibliographically approved