GranÚli, E. Dept. of Marine Sciences, University of Kalmar, edna.graneli@ng.hik.se
Carlsson, P. Dept. of Marine Sciences, University of Kalmar, per.carlsson@ng.hik.se
Legrand, C. Dept. of Marine Sciences, University of Kalmar, catherine.legrand@ng.hik.se
Johnsen, G. Norwegian University of Science and Technology, geir.johnsen@vm.ntnu.no
Luckas, B. Inst. of Nutrition and Environment, University of Jena, b5belu@rz.uni-jena.de
Reichelt, M. Inst. of Nutrition and Environment, University of Jena, b5mire@rz-uni-jena.de

 
STRUCTURATION OF MARINE PHYTOPLANKTON COMMUNITIES SUBJECTED TO DIFFERENT LEVELS OF N, P AND SI LIMITATION IN A MESOCOSM EXPERIMENT
 
During July 1998 a mesocosm experiment was performed with Baltic sea water in order to investigate how different nutrient ratios and concentrations would affect (1) the structuration of the phytoplankton species composition and, (2) at which nutrient condition algal toxin content would be highest. Polythene cylinders (300 l) filled with seawater were exposed to light and temperature imitating the 10 m depth from where the water was sampled. Nitrogen, phosphorus and silicon were added as daily pulses at 2 different levels of limitation to 3 replicates of each treatment. Also, a nutrient balanced treatment (according to the Redfield ratio) was used as control. Nitrate was the only nutrient that reached undetectable concentrations at both limiting levels (1.6 and 4.8 ÁM N added/day). The lowest concentrations of chlorophyll a and carbon uptake were found in the cylinders were nitrate was added at the lowest addition at the end of the experiment. In the cylinders where the phytoplankton communities were P-limited, the cyanobacteria-species Nodularia spumigena and Anabaena sp. dominated and not in the nitrogen limited as expected.
 
Day: Thursday, Feb. 4
Time: 11:45 - 12:00pm
Location: Eldorado Hotel
 
Code: SS51TH1145E