The UK is an island nation and our cultural identity is tightly linked to the sea. As well as being home to a bounty of wildlife, ranging from intricate intertidal invertebrates to bustling seabird colonies, our marine ecosystems provide a multitude of services including fisheries and carbon sequestration. The UK marine environment however, faces ongoing pressures as a result of varied and cumulative human activities, as well as undergoing fundamental restructuring as a result of climate change. Given our connection to the marine environment, and these ongoing pressures, an assessment of the state of nature for the UK must include marine as well as terrestrial biodiversity. An up-to-date overview of the state of marine biodiversity is therefore included in the RSPB State of Nature report for 2019 (embargoed until Oct 4, 2019).

Marine biodiversity in the UK is monitored and assessed under an overarching framework called the UK Marine Strategy. The aim of the UK Marine Strategy is to achieve a sustainable, balanced level of human activities that allows marine biodiversity to flourish and the flow of ecosystem services to be sustained. To develop the Marine Strategy, a concerted effort has been undertaken to develop a suite of indicator metrics for different components of the marine ecosystem. In order to ensure alignment with this key policy framework, the State of Nature report drew on these indicator metrics for reporting on marine biodiversity trends. Data that inform these indicators for the State of Nature assessment came from a variety of sources.

For example data on plankton, which form the base of the marine ecosystem, was provided by the Continuous Plankton Recorder survey. The CPR survey has been monitoring UK phytoplankton and zooplankton communities since 1931, with consistent, comparable data available since 1958. This unique 60 year time-series has been achieved through partnerships with ‘ships of opportunity’ including passenger ferries and cargo ships, which allows a collection of plankton samples at large spatial scales.

The CPR survey has revealed key plankton trends, largely related to the signals of climate change. These include an increase in the proportion of warmer water copepod species with increasing Sea Surface Temperatures, and an increase in the Phytoplankton Colour Index (PCI), which measures the ‘greenness’ of the silk of each CPR sample, and is a proxy for total phytoplankton biomass. As shown in the State of Nature report, this index has shown a clear increasing trend in UK seas since 1958. For example, in the Northern North Sea, the PCI is 67% higher than it was in the 1960s.

The reporting on trends in the composition of plankton communities followed the UK Marine Strategy by aggregating individual taxa into broad functional groups known as lifeforms. In contrast to conserving the populations of birds and mammals, when assessing and managing plankton biodiversity the emphasis is on maintaining a healthy community composition, rather than maintaining high abundance and richness. Through monitoring the relative abundance of different lifeforms, changes in the structure and functioning of lower trophic levels can be monitored. For example, small and large copepods are two key functional groups of zooplankton that have different roles in the ecosystem and may support different trophic pathways.  As functional changes in plankton, such as the size composition of copepods, can affect higher trophic levels, plankton lifeforms help provide context for marine conservation and management.

The State of Nature report highlights the complex and interactive drivers affecting marine ecosystems. As well as large-scale climate change trends, fishing continues to damage the seafloor and alter the size composition of fish communities, although recovery in abundance is shown for many fish species from historical over-exploitation. Noise and plastic pollution are also emerging threats. Moving forward, it is crucial that these cumulative impacts on biodiversity are tackled through innovative and progressive management interventions. For example, it is highlighted in the report that although management measures have been documented in 60% of Marine Protected Areas (MPAs) in the UK, they are only fully implemented in 10% of sites.  By fully adopting an ecosystem approach, for example through well-enforced, whole-site based MPA management, declines in key habitats and species can be halted. This in turn will help build resilience in the ecosystem to future climate change.

Jake, Plankton and Policy

Read more:

Bedford, J., Johns, D., Greenstreet, S. and McQuatters-Gollop, A., (2018). Plankton as prevailing conditions: a surveillance role for plankton indicators within the Marine Strategy Framework Directive. Marine Policy, 89: 109-115.

Capuzzo, E., Lynam, C.P., Barry, J., Stephens, D., Forster, R.M., Greenwood, N., McQuatters-Gollop, A., Silva, T., Sonja M. van Leeuwen and Engelhard, G.H., (2018). A decline in primary production in the North Sea over 25 years, associated with reductions in zooplankton abundance and fish stock recruitment. Global Change Biology, 24: e352-e364.

McQuatters-Gollop, A., Atkinson, A., Aubert, A., Bedford, J., Best, M., Bresnan, E., Cook, K., Devlin, M., Gowen, R., Johns, D.G., Machairopoulou, M., Mellor, A., Ostle, C., Scherer, C. and Tett, P., (2019). Plankton lifeforms as a biodiversity indicator for regional-scale assessment of pelagic habitats for policy Ecological Indicators, 101: 913-925.

McQuatters-Gollop, A., Edwards, M., Helaouët, P., Johns, D.G., Owens, N.J.P., Raitsos, D.E., Schroeder, D., Skinner, J. and Stern, R.F., (2015). The Continuous Plankton Recorder survey: how can long-term phytoplankton datasets deliver Good Environmental Status? . Estuarine, Coastal and Shelf Science, 162: 88-97.