Using environmental DNA to understand the role of connectivity in pond ecosystems

The majority of freshwater habitats are small in scale, comprising ponds and low-order streams, ditches and springs. Collectively these represent the largest resource of freshwater habitats across the UK and provide a heterogeneous network of resources for a wide diversity of freshwater and terrestrial organisms. However, man-made environmental change is having substantial negative impacts on freshwater ecosystems, with small waterbodies being particularly vulnerable to change. As a result, freshwater habitats have experienced disproportionate declines in biodiversity. These habitats do not exist in isolation and are frequently a part of a mosaic of sites that are interconnected both hydrologically and ecologically. This connectivity is a critical component in maintaining freshwater biodiversity, as connected metacommunities of organisms allow for the exchange of individuals between sites, which can contribute to ecosystem stability at multiple scales. A major challenge to understanding the role that connectivity has in structuring freshwater ecosystems is that describing and quantifying biodiversity is extremely challenging. As a result, most studies have focused on easily identified species. However much freshwater biodiversity comprises small, morphologically conserved organisms that are difficult to identify. This project will seek to address these issues by applying DNA metabarcoding to examine pond biodiversity across trophic levels, including bacteria, phytoplankton, invertebrates and vertebrates. This multi-tropic characterisation will reconstruct whole pond ecosystems, examining interactions and the stability of networks within and across ponds.
The first year of the project will involve intensive sampling at Freshwater Habitats Trust (FHT) Pinkhill Meadows Flagship Ponds site to calibrate and test the molecular approaches across a small landscape of hydrologically interconnected ponds. Year two will focus on a network of small water bodies of varying connectivity, landscape permeability and environmental character (e.g. one of the FHTs Flagship Pond sites such as the Norfolk Pingos, New Forest Ponds, or Welsh Upland Ponds) with locations to be decided by the student in consultation with the supervisory team. Molecular work, bioinformatics and analysis will be carried out at the state-of-the-art molecular ecology facility at CEH Wallingford, with secondments to Cardiff University to spend time with the co-supervisor (Steve Ormerod) to develop analysis and interpretation skills in freshwater ecology, and with the project partner Jeremy Biggs at the Freshwater Habitats Trust who has extensive experience of sampling and understanding the ecology of pond ecosystems. The FHT work to conserve freshwater ecosystems, and the data generated in this project will be used by the project partner to better understand the value of Flagship Pond sites and how best to conserve them in light of the multiple pressures they face.