The primary production of phytoplankton in the restored Maltanski Reservoir in Poland

The paper presents the results of the seasonal fluctuation of planktonic primary production (gross and net), respiration and photosynthetic activity of water in the completely restored Maltanski Reservoir in Poznan (mid-west Poland), in which a biomanipulation experiment was conducted. Water samples were taken from 1992 to 1997 every month or in vegetation seasons every fortnight. Primary production measurements were made in a deep section of the reservoir with 1-meter intervals between surface and 3-meter depth, using dark and light bottles (oxygen-technique). Maximal productivity was noted in the surface layer of the reservoir with wide seasonal variation: from 0.1 to 6.8 mg C l(-1) d(-1) and from 0.08 to 4.7 g C m(-2) d(-1). The highest monthly average values of primary production were observed in summer when cyanobacteria were dominated. The phytoplankton productivity was significantly correlated with water temperature, insolation, Secchi depth and chlorophyll-a. Only weak correlation of primary production and total phosphorus was noted. Biomanipulation experiment carried out in the reservoir led to temporary decreasing of primary production in 1993 and increasing specific primary production, up to 14.1 mug C mug Chl(-1) h(-1).