eDNA Enhances Marine Monitoring and Reveals Climate-Driven Ecosystem Change in the Western English Channel

Authors: Karen Tait1*, Angus Atkinson1, Pennie Lindeque1, Sebastian Mynott2, David Sims3 

*Corresponding author. 

Affiliations: 1Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH United Kingdon; 2Applied Genomics Ltd, Brixham Environmental Laboratory, Freshwater Quarry, Brixham TQ5 8BA, United Kingdom; 3Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth, PL1 2PB, UK. 

Marine policy and ecosystem management require observing systems capable of detecting biodiversity change and identifying the mechanisms driving ecosystem responses to climate change. The Western Channel Observatory provides a unique long-term reference site where environmental DNA (eDNA) sampling is undertaken alongside established monitoring, enabling an assessment of how molecular approaches can strengthen marine observation programmes.  

Analysis of 425 paired zooplankton samples collected over 11 years showed strong agreement between eDNA and microscopy for major holoplanktonic groups. Beyond corroborating established observations, the higher taxonomic and trait resolution provided by eDNA revealed that reported increases in meroplankton were driven primarily by soft-sediment filter-feeding taxa rather than direct warming effects. These findings point to broader food-web restructuring associated with declining nutrient supply and a shift towards smaller phytoplankton.  

Across the fish community, multiple independent indicators converged on the same signal of ecological change. eDNA, fish egg and larval observations, acoustic observations, and biomass size spectra all revealed declining diversity, reduced support for early fish life stages, and increasing dominance of short-lived pelagic species such as sardine and anchovy. The agreement among fundamentally different monitoring approaches increases confidence that these trends reflect genuine ecosystem restructuring rather than methodological artefacts. 

Together, these results demonstrate how integrating eDNA within long-term observing programmes can improve detection, interpretation and assessment of climate-driven ecosystem change, strengthening the evidence base for adaptive management and biodiversity policy.