Abstract
Environmental DNA (eDNA) has been used in a variety of ecological studies and management applications. The rate at which eDNA decays has been widely studied but at present it is difficult to disentangle study-specific effects from factors that universally affect eDNA degradation. To address this, a systematic review and meta-analysis was conducted on aquatic eDNA studies. Analysis revealed eDNA decayed faster at higher temperatures and in marine environments (as opposed to freshwater). DNA type (mitochondrial or nuclear) and fragment length did not affect eDNA decay rate, although a preference for <200 bp sequences in the available literature means this relationship was not assessed with longer sequences (e.g. >800 bp). At present, factors such as ultraviolet light, pH, and microbial load lacked sufficient studies to feature in the meta-analysis. Moving forward, we advocate researching these factors to further refine our understanding of eDNA decay in aquatic environments.