Microscopic plankton are among the most important organisms on Earth. Phytoplankton produce around half of the oxygen we breathe, while plankton as a whole underpin marine food webs, support fisheries, help regulate carbon, and sustain life across the ocean.
However, a new study - led by researchers at the University of Plymouth - has used more than six decades of data to show that plankton abundance is declining across vast swathes of the North East Atlantic – a region covering the Atlantic Ocean from Portugal to Norway, and the entirety of the North Sea.
The research used 23 plankton datasets from 13 research institutions, alongside satellite data, to generate the first ever quantitative and integrative assessment of whether the pelagic habitats of western Europe are in Good Environmental Status, as defined by the EU and UK Marine Strategy Framework Directive.
These habitats are the open-water regions dominated by plankton and are central to ocean functioning. However, until now assessments for policy have largely described changes in plankton without being able to integrate them quantitatively into a clear regional status assessment.
This new work filled that gap by combining monitoring data from assessment units and fixed-point stations, with scientists then integrating that status across plankton indicators and habitat types to derive regional environmental status.
The results showed there were no pelagic habitats anywhere in the North East Atlantic rated as good, with six pelagic habitat-region combinations assessed as ‘Not Good’, three as ‘Uncertain’, and one ‘Unassessed’ due to lack of data.
At regional scale, the Celtic Seas and the Bay of Biscay and Iberian Coast were assessed as ‘Not Good’, while the Greater North Sea was assessed as ‘Uncertain’. The poorest status was generally found in shelf habitats, where changes in plankton communities and declines in phytoplankton biomass and zooplankton abundance were most clearly detected.
The research also found rising sea surface temperatures, changing nutrient conditions, declining pH, and altered ocean mixing to be among the key factors associated with changes in plankton and their habitats.
As a result, the researchers say the most important action to protect the functioning of pelagic habitats is to mitigate ongoing climate change through supporting global reductions in carbon emissions.
They have also called for stronger action to reduce nutrient pollution, particularly nitrogen, and for sustained investment in plankton monitoring. Several long-term plankton time-series in the OSPAR assessment area are currently paused or at risk due to reduced resources, despite being essential for detecting ecological change and informing marine policy.
The paper, published in the journal Ecological Indicators, was led by
Professor Abigail McQuatters-Gollop and involved a consortium of European universities, science organisations and environmental agencies.
Professor Abigail McQuatters-Gollop
