The effect of synthetic anionic surface active substance (SAS) sodium dodecylsulfate (SDS, 4 mg/l) on the kinetics of water filtration by mussel Mytilus edulis was studied. A suspension of algae Isochrysis galbana was added to the vessel with the mussels, and their filtration activity was measured by counting the concentration of the algae cells in the experimental vessels. Algae concentration was measured every 30 min for an hour and a half. The inhibiting effect on the mollusk filtration rate (FR) was qualitatively described. After the first 30 min filtration at 4 mg/l initial SDS concentration, the cell density was 322% of the control. The inhibiting effect was observed later as well. Due to FR inhibition in the vessels with the above specified initial SDS concentration, the algae cell density was 6.4 and 14.7 times that of the control after 1 and 1.5 h, respectively. Thus, SAS SDS can decrease the natural capacity of aquatic ecosystems for self-purification and disturb other aspects of ecosystem functioning through inhibiting the filtration activity of mussels. The obtained data are discussed in the context of environment and hydrosphere protection from pollution.