Assessment of the Colonization and Primary Production of Microphytobenthos in the Littoral of Acidic Mining Lakes in Lusatia (Germany)

In 3 extremely acidic mining lakes (pH 2.6-3.1) in Lusatia (Brandenburg, Germany) microphytobenthos colonization was characterized by a very low species diversity, and partly high abundances of the dominant species. Eunotia exigua (Bacillariophyceae) was frequent in all lakes. The abundance of Nitzschia paleaeformis (Bacillariophyceae) clearly increased with increasing pH. Euglena mutabilis (Euglenophyceae) occured mainly in the littoral of Lake 108 with a strongly varying spatial and temporal distribution. Mean concentrations of microphytobenthic biomass, measured as chlorophyll a (Chl), showed marked variations between the lakes and ranged between 1.3 - 17.9 µg Chl g dw-1 or 5.1 - 120 mg Chl m-2. Primary production of microphytobenthos was measured using polyethylene foils as artificial substrates or by direct measurements of sediment surface samples. Primary production rates and specific production rates ranged between 0.99 - 5.1 mg C m-2h-1 and 0.04 - 0.33 mg C (mg Chl)-1h-1, respectively. The impact of the sediment chemistry (especially the available carbon) is discussed as determining factor for the species composition and activity of the microphytobenthic species. First insights can be given concerning the relevance of benthic algae for the carbon metabolism of the investigated acidic mining lakes.