The aim of the conducted research was to determine the possibilities of using the biomass of macroalgae obtained from Puck Bay during May-September season in biogas production process. Model respirometry chambers were used to determine the amount of produced biogas and examine its quality composition. Depending on the month in which the algal biomass was obtained, the experiments were divided into five stages. In each stage, the effectiveness of the biogas production process was tested for the applied loads in model fermentation chambers in the range from 1.0 kg DOM/m3 · d to 3.0 kg DOM/m3 · d. During the experiments it was found that the efficiency of biogas production varied from 205 dm3/kg DOM to 407 dm3/kg DOM depending on the month of the vegetation season and the applied organic matter load in the chamber. Methane content was very high and ranged from 63% to 74%.

Silicon, an important clement for diatoms, is often beyond the main object of freshwater researches. In the last decade, many detergents containing silicon compounds have been released by municipal sewage to surface water ecosystems. In this paper, an influence of silicates and washing agents which contain silicates on algal primary production and biomass growth has been shown. The experimental analysis revealed that detergents with the silicate addition increased the rate of the biomass growth and had a direct impact on algal primary production.