Environmental DNA (eDNA) holds great potential for biomonitoring and ecological research. However, its utility for quantifying temporal changes in abundance, biomass, and diversity remains contentious. In this thesis, I investigated biotic and abiotic factors influencing temporal and spatial variation in eDNA concentration. Time series data demonstrated a positive relationship between the population abundance of the cladoceran zooplankton species Daphnia magna and its eDNA concentration in large aquatic mesocosms, with a time lag of ~ 3.5 days. Environmental temperatures of 15 °C promoted greater eDNA persistence than metabolically favorable (25 °C) conditions. Levels of spatial autocorrelation suggest that the swimming activity of Daphnia and/or thermally-driven mixing might have homogenized the distribution of their eDNA over the entire water column.