SS4.09 Does Intentional Nutrient Fertilization (N,P And Fe) Foster C Sequestration and/or Increased Fish Fertilization?
Date: Tuesday, June 11, 2002
Time: 10:15:00 AM
Location: Colwood
 
VredeT, Uppsala University, Dept. of Limnology, Uppsala, Sweden, tobias.vrede@ebc.uu.se
Persson, J, , Uppsala University, Dept. of Limnology, Uppsala, Sweden, jonas.persson@ebc.uu.se
Sobek, S, , Uppsala University, Dept. of Limnology, Uppsala, Sweden, sebastian.sobek@ebc.uu.se
Blomqvist, P, , Uppsala University, Dept. of Limnology, Uppsala, Sweden, peter.blomqvist@ebc.uu.se
Jansson, M, , Ume Univ., Dept. of Ecology and Environmental Science, Ume, Sweden, mats.jansson@eg.umu.se
Tranvik, L, , Uppsala University, Dept. of Limnology, Uppsala, Sweden, lars.tranvik@ebc.uu.se
 
RESPONSE OF PLANKTON TO NUTRIENT ENRICHMENT
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The response of plankton to N and P enrichment was studied in mesocosms in an ultra-oligotrophic sub-alpine reservoir. The experiment had an unreplicated factorial design with 4 levels of P addition (0-12 g/l), and 3 levels of N addition (0-80 g/l). The results will be used in the dimensioning of future fertilization of the reservoir to increase the production of salmonid fish. P had a positive effect on phytoplankton (mainly edible mixotrophic flagellates) and protozoan biomass, particulate C, and bacterioplankton production. In contrast, N had no effect on these variables. CO2 was negatively correlated with chlorophyll a, indicating a shift towards net autotrophic conditions upon P enrichment. The response to P addition was non-linear, with only moderate or no increase in biomasses at P doses of 8 and 12 gP/l compared with treatments with an P addition of 4 gP /l. A possible explanation for this weak response is trace element deficiency at high P doses.