Test-casing the integration of plankton imaging and genomics data for biodiversity indicator assessments in the Southern North Sea

Planktonic organisms are the most abundant organisms in the oceans and are considered excellent indicators for environmental changes; they are the basis of the food web and, thus, ecosystem functioning. Changes in plankton diversity have been used extensively as an indicator of ecosystem health. Plankton assessment is included in two of the Essential Ocean Variables (EOVs), as well as in the assessment Good Environmental Status under Marine Strategy Framework Directive (MSFD). The aim of this study was to test-case eDNA-based biodiversity observations from a large-scale long-term monitoring network, i.e. the European Marine Omics Biodiversity Observation Network (EMO BON), against image-based observations to identify the potential for eDNA to serve as an input source for EOV assessments or MSFD indicators’ calculation. We used phyto- and zooplankton imaging data collected from seventeen stations monitored on a monthly or seasonal basis and eDNA data collected bi-monthly from one EMO BON observatory, in the Belgian part of the North Sea (BPNS). This (proof of concept) study is a practical assessment of the suitability and validity of eDNA data for calculation of plankton-based indicators and EOVs. The validity of the information deriving from both methods allows a holistic understanding of coastal biodiversity status.