Understanding eDNA decay in aquatic environments

Environmental DNA (eDNA) is DNA or genetic material released from an organism into its environment (soil, water, air) and provides trace evidence of its current or past presence in that environment. This can include the organism’s faeces, urine, gametes and mucous or their decaying remains. eDNA is increasingly being used to detect the presence of species and assess biodiversity in different ecosystems but best practices are still being developed. This affects the quality, accessibility and usefulness of data.

The rate of eDNA degradation has been extensively researched, although it is currently challenging to distinguish study-specific effects from those that influence eDNA degradation universally. To address this, a recent study conducted a systematic review and meta-analysis on aquatic eDNA studies. According to the analysis, eDNA degraded more quickly in marine environments and at higher temperatures than in freshwater. DNA type (mitochondrial or nuclear) and fragment length did not affect eDNA decay rate, although a preference for <200 base pair (bp) sequences in the available literature means this relationship was not assessed with longer sequences (e.g. >800 bp). Currently, there aren’t enough studies on variables like pH, UV light, and microbial load to be included in the meta-analysis. In order to improve our knowledge of eDNA degradation in aquatic environments, the researchers recommended more research on these variables.

AquaPLAN partner Ban Ilan University (BIU) will quantify how eDNA is affected by light and noise pollution (LNP) in the coral reef ecosystem of the Gulf of Eilat/Aqaba. This will be done using ceramic terracotta tiles and collecting water samples over a period of 24 months (intervals of 4 months) in both in situ and aquarium systems with running seawater. Leibniz Institute of Freshwater Ecology and Inland Fisheries (FVB-IGB) will help to quantify the light environments above and in the water column, while University of Pisa (UNIPI) and Stazione Zoologica Anton Dohrn (SZN) will help with noise manipulation and bioacoustics sampling activities. The coral reefs in the Gulf of Eilat/Aqaba are located in the northernmost part of the Red Sea and experience little to no bleaching effects.

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