The phenology of environmental DNA detection for coastal aquatic invasive species

Abstract

Environmental DNA (eDNA) has transformed aquatic invasive species (AIS) surveillance, yet the temporal ecology of eDNA signals remains poorly understood. Here, we introduce the concept of “eDNA phenology” to describe predictable seasonal variation in eDNA detectability arising from interactions among species life history, environmental conditions, and the ecological processes governing DNA production, transport, and persistence. We investigated weekly eDNA dynamics (2, 663 samples) of five coastal AIS ( Botrylloides violaceus, Didemnum vexillum, Ciona intestinalis, Membranipora membranacea , and Carcinus maenas ) across five locations spanning a broad latitudinal gradient in the Northwest Atlantic using year-round, species-specific qPCR monitoring. Despite substantial ecological differences among taxa, species exhibited coherent regional phenological patterns, with predictable latitudinal shifts in seasonal eDNA abundance. Seasonal and regional effects explained most variation in eDNA dynamics, whereas instantaneous environmental variables provided comparatively modest additional explanatory power. Comparisons with conventional settlement monitoring further showed that eDNA signals frequently preceded or extended beyond observable settlement periods, suggesting that eDNA captures ecological dynamics not fully resolved by organismal observations alone. Together, these findings highlight that environmental and temporal variability should be considered when interpreting relationships between eDNA concentration and species abundance. Quantifying eDNA phenology provides a predictive framework for interpreting species ecology beyond simple detection and for improving the design, sensitivity, and forecasting capacity of biodiversity surveillance.