EUTROPHICATION PROCESSES IN A SHALLOW, MACROPHYTE-DOMINATED LAKE SPECIES DIFFERENTIATION, BIOMASS AND THE DISTRIBUTION OF SUBMERGED MACROPHYTES IN LAKE-LUKNAJNO (POLAND)

In Lake Luknajno submerged macrophytes occupied 50% of lake area and t heir mean biomass was 350 g dry weight m(-2) in the 1993 year. Maximum biomass values of charophytes reached high levels above 1000 g dry we ight m(-2) (in a few samples). During the last 20 years changes in sub merged macrophytes were mainly quantitative. In that period the area o ccupied by plants decreased twice, presumable by eutrophication. In 19 93 Lake Luknajno was still a Chara-type. Seven species of Characeae we re recorded, Chara aculeolata and C. tomentosa being the most abundant . The contribution of charophytes to total dry weight of all submerged macrophytes was 90%. At stations covered with Chara, phosphorus, nitr ogen and chlorophyll concentrations were markedly lower than at statio ns devoid of plants.