AbstractEnvironmental DNA (eDNA) holds notable potential for biomonitoring and ecological research. However, its utility for quantifying temporal changes in abundance, biomass, and diversity remains contentious. We investigated biotic and abiotic factors influencing temporal variation in eDNA concentration in large, 28,000 L experimental mesocosms. Time series data demonstrated a positive relationship between the population abundance and biomass of the Cladoceran zooplankton species Daphnia magna and eDNA concentration, with a time lag of ~3.5 days in 25°C conditions, and up to 28 days in 15°C. Water temperature variations within mesocosms did not consistently influence eDNA quantity, although water temperature negatively predicted DNA concentration across mesocosms. Algal density negatively correlated with D. magna eDNA quantity across and within mesocosms. We demonstrate that eDNA signal detection can be used as a proxy for relative abundance and suggest that future investigation into the dynamics of eDNA shedding and degradation processes is warranted.