Monitoring intertidal biodiversity in a changing climate using visual and environmental DNA surveys

Simons, Dina ORCID: 0000-0002-1898-1738 (2026) Monitoring intertidal biodiversity in a changing climate using visual and environmental DNA surveys PhD thesis, University of Liverpool.

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Abstract

Climate change alters thermal regimes in coastal ecosystems, affecting the reproduction and survival of marine species. These impacts are most pronounced at the edges of an organism's habitable range where environmental variables, such as temperature, approach physiological limits. Tracking how species relocate along coastlines provides valuable insight into climate-driven change. Rocky intertidal species are particularly sensitive to warming and act as effective indicators of shifts in the structure and function of marine communities. Although visual surveys are widely used for monitoring, they are labour intensive, difficult to scale up, and often miss elusive species. Environmental DNA (eDNA) methods might improve the resolution and scope of biodiversity monitoring in intertidal habitats, yet field-based assessments of their reliability in these dynamic environments remain limited. This thesis evaluates the application of eDNA technologies for monitoring rocky intertidal biodiversity in light of climate change. By conducting the first nationwide intertidal eDNA sampling effort around the UK coastline, the thesis assesses the detection capacity of eDNA at multiple spatial scales, compares eDNA-derived detections with existing visual data, and incorporates eDNA data into species distribution models. The thesis aims to determine whether eDNA is a viable tool for detecting changes in intertidal communities and, if so, propose a pathway to integrate eDNA methods with existing methods. Broadly targeting marine invertebrates and macroalgae, a total of 262 onshore water samples were collected alongside co-located visual surveys from 32 rocky shore sites across five UK Regional Seas. Firstly, eDNA analyses identified more than 1,000 relevant taxa, revealing distinct community patterns at all spatial scales, including variation within sites across abiotic gradients. Detections from eDNA also matched known ecological patterns at both local and national scales. Secondly, there was moderate concordance between eDNA and visual detections, with each detecting certain groups of species more effectively than the other. Visual surveys captured more species-level detections for key indicators, while eDNA revealed additional unmonitored taxa across relevant phyla and showed higher sensitivity for 12 inconspicuous species. Thirdly, species distribution models combining eDNA and visual data performed comparably to those based solely on visual records, accurately representing thermal ranges and predicting realistic climate-driven range shifts for two intertidal barnacles with opposing thermal affinities. Overall, this thesis supports emerging evidence that eDNA has strong potential for multiscale biodiversity monitoring in dynamic marine environments. It also suggests that combining monitoring methods will provide a more comprehensive representation of rocky shore biodiversity. The thesis demonstrates the reliable use of eDNA data in habitat suitability models to predict current and future distributions. The research provides practical recommendations for optimising eDNA sampling on rocky reefs and contributes various ecological and methodological insights across its chapters. Evidence-based recommendations are provided for scale-appropriate eDNA sampling, supporting the integration of eDNA with visual surveys for more comprehensive monitoring. These findings can inform the future design of national monitoring programmes, helping to use novel molecular approaches to track climate-driven biodiversity change.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	climate change, eDNA metabarcoding, environmental DNA, intertidal, marine biodiversity, molecular monitoring, rocky shores
Divisions:	Faculty of Science & Engineering Faculty of Science & Engineering > School of Environmental Sciences
Depositing User:	Symplectic Admin
Date Deposited:	07 Apr 2026 13:04
Last Modified:	07 Apr 2026 14:21
DOI:	10.17638/03197090
Supervisors:	Mieszkowska, Nova Spencer, Matthew Hipperson, Helen Webb, Tom
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3197090
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