Species-specific differences in phytoplankton responses to N and P enrichments and the N:P ratio in the Archipelago Sea, northern Baltic Sea

• Published in: Journal of plankton research Vol. 26; no. 7; pp. 779 - 798
• Main Authors: Lagus, A., Suomela, J., Weithoff, G., Heikkilä, K., Helminen, H., Sipura, J.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.07.2004; Oxford Publishing Limited (England)
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Archipelagoes; Bacillariophyceae; Bacteria; Biological and medical sciences; Chaetoceros; Chlorophyll; Chlorophylls; Diatoms; Feed composition; Fundamental and applied biological sciences. Psychology; Marine; Nutrient cycles; Nutrient enrichment; Phosphorus; Phytoplankton; Sea water ecosystems; Skeletonema costatum; Species; Synecology; Uroglena; Baltic Sea; ANE, Baltic Sea; Marine environment; Medium enrichment; Plankton; Growth; Interspecific comparison; Environmental factor; Phosphorus; Phytoplankton; Nitrogen
• DOI: 10.1093/plankt/fbh070
• ISSN: 0142-7873; 1464-3774

A nutrient enrichment experiment was conducted in order to study the role of nitrogen (N), phosphorus (P) and the N:P ratio on the early summer phytoplankton community in the Archipelago Sea, northern Baltic Sea. The phytoplankton community was, in terms of chlorophyll a and total biomass, primarily N-limited, but the individual species varied in their responses to the nutrient supply. The recorded overall N limitation was due to fast growth responses of a few N-limited species such as the diatom Chaetoceros wighamii (Brightwell) and the mixotrophic chrysophyte Uroglena sp. Another dominating diatom, Skeletonema costatum (Greville) Cleve was most clearly P-limited. The N:P ratio had the strongest effect on Uroglena sp., which grew exponentially in the enrichments with a high N:P ratio. This can be explained by the ability of the species to feed on P-rich bacteria, which gives it a competitive advantage in P-limited conditions. The species-specific differences in the responses to the nutrient enrichments can generally be explained by differences in the species physiology and they were consistent with the theory of resource competition.