Spatial and seasonal variability in extracellular leucine aminopeptidase and lipase activity in Baltic Sea beach sand with different levels of anthropopressure

Measuring extracellular hydrolytic enzyme activity can provide a fundamental understanding of the biogeochemical cycling of organic matter in freshwater and marine basins. We investigated the level of leucine aminopeptidase, lipase activity, and their spatial and seasonal variability across 3 sandy beaches on the southern Baltic Sea. These beaches differed in the degree of anthropogenic pressure. The results showed that lipase activity was about 4-10 times higher compared to leucine aminopeptidase activity in the sand of all studied beaches. The activity level of these 2 hydrolases depended on the degree of anthropogenic pressure. In the sand of the beach subjected to high anthropopressure, the activity of both hydrolytic enzymes was the highest. The enzymatic activity also varied along the horizontal and vertical profiles of the beaches. The 2 studied enzymes typically showed their maximum activity in the dry zones and minimum in the wet zones of the profile perpendicular to the shoreline. The highest level of leucine aminopeptidase and lipase activity in all studied beaches was determined in the surface sand layer of the vertical profile. A seasonal variation in the activity of the 2 studied hydrolases was also documented.