Fluctuations and interactions of bacterial activity in sandy beach sediments and overlying waters

Fluctuations and interactions of the following microbiological variables and sediment properties were investigated on samples from sandy beaches of the Baltic Sea: bacterial number and biomass, net uptake and respiration rate of ¹⁴C-glucose (U), concentration of natural free dissolved glucose and fructose, actual uptake rate and turnover time of glucose, sand-grain size and shape, water and organic matter content of the sediment. Spearman rank correlation analysis demonstrated significant relationships between cell number, biomass and actual uptake rate of glucose. The concentration of natural glucose varied with sand-grain shape, and the uptake rates of glucose were inversely correlated with the water content of the sediment. In the overlying water, cell number and/or biomass were significantly correlated with both concentration and uptake rates of glucose. Partial correlation analysis, however, indicates that, in the water overlying the sediment at least one of the standing crop variables (bacterial number or biomass) is independently variable with uptake activity. The sediment bacterial standing crop does not necessarily reflect metabolic activity. Various significant interactions were noted between mainly sediment properties (water content, organic matter content, grain size) and variables in the water above (cell number, biomass, concentration and uptake rates of glucose).Publication No. 206 of the Joint Research Program at Kiel University (Sonderfor-schungsbereich 95 der Deutschen Forschungsgemeinschaft).