eDNA

Using DNA to study marine ecosystems can offer a glimpse of complete ecosystems at phenomenal resolution. So-called environmental or eDNA approaches have the potential to provide unprecedented detail and insight into the abiotic and biotic drivers that influence community structure and diversity, unravelling the ecological connections between taxa and their environment at a fraction of the sampling cost of traditional methods such as time-consuming microscopy. Valuable data on groups that are hard to identify without specialist knowledge, are difficult to sample, are rare or are previously unstudied can all be identified with ease.

However, there remains a great deal of uncertainty over how eDNA data can be interpreted. Investigations are ongoing by PML experts to provide a thorough comparison of data derived from traditional methods with that provided using eDNA. At the Western Channel site L4 we have gathered eight years of eDNA and traditionally collected morphological samples (e.g. microscopically identified) and are using this data to identify the gaps and synergies between morphological and molecular data sets. This approach is currently being used to gain enhanced insight into the prevalence and temporal dynamics of harmful algae. Data from across the NW European shelf are showing a decline in chlorophyll and increases in the abundance of meroplankton (animals that have both planktonic and benthic stages in their life cycle), suggesting a major re-organisation in the balance between pelagic- and benthic production is occurring. At PML, we are using our molecular timeseries data to identify meroplankton species present at L4, providing valuable insight into the functional traits of winners and losers in a changing world.

Through sequencing eDNA and modelling stable isotope data for over a year PML-led research showed, for the first time, the important role the connectivity between macroalgae (seaweed) and the seabed plays in permanently removing carbon dioxide from the atmosphere. This has crucial implications for efforts to reduce emissions in light of the Paris Climate Agreement, and how we manage the environmentally and economically important marine habitats.

PML’s research methods are transferable across the globe, from estuarine to coastal, pelagic and benthic, and at a range of temporal resolutions. Demonstrated such as through ongoing research in the Arctic where PML is using genetic characters (much as we employ DNA fingerprinting for identifying individual humans) for unambiguous identification of copepods, an important food web species, providing information which would not be obtained through traditional sampling and observation methods. Further PML research is employing eDNA methodologies to determine the influence of sea ice change on the types and possible sources of both marine and terrestrial inputs to the sea floor.

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