The decline in plankton abundance in the North East Atlantic over the past six decades should serve as a red flag to policy makers about the need to protect some of the planet's most critical forms of life, a new study has warned.
Scientists from across western Europe carried out the most comprehensive assessment to date of long-term changes in the region's plankton communities.
They analysed 24 phytoplankton and zooplankton datasets generated by 15 research institutions to map the 60-year abundance trends for eight planktonic lifeforms.
This included data collected by the Continuous Plankton Recorder (CPR) Survey, which has been operating since 1931 and represents the most geographically extensive marine monitoring programme in the world.
Across the open oceans of the North East Atlantic, where temperatures have increased gradually during the past six decades, most of the lifeforms assessed showed a decrease in abundance.
Dinoflagellates (an important type of phytoplankton), for example, have decreased by around 5% per decade since the 1960s while the quantities of holoplankton (zooplankton that spend their entire lives in the water column) fell by 7% per decade.
By contrast, similar populations in the North Sea - which has undergone major warming, changes in nutrients, and disruption from fisheries - have remained far more stable. Some plankton populations there, and particular in more coastal regions, have even increased in abundance.
Writing in the journal Science of the Total Environment, the study's authors say the reasons behind the variation in impacts from the North East Atlantic to the North Sea are not wholly clear, but align with a rise in human use of the oceans and an acceleration in changes to the global climate.
They also say that with plankton playing such an integral role in the food chain - and phytoplankton, in particular, generating up to 50% of the planet's oxygen - the decline represents a cause of major concern.
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