Six decades of decline sparks call to protect the foundation of the marine food web
Plymouth researchers have published research showing the impact of human activities and climate change on plankton in the North East Atlantic
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.
Study lead author Dr Matthew Holland, a Postdoctoral Research Fellow from the Marine Conservation Research Group at the University of Plymouth, said: “Plankton form the base of marine food webs, making them important indicators of ecosystem status. Changes in the abundance of plankton functional groups, or lifeforms, can affect higher food web levels and indicate important shifts in ecosystem functioning. With our study highlighting major changes over a prolonged period of time, it should provide a red flag to politicians and policymakers about the prioritisation of future management and adaptation measures required to ensure future sustainable use of the ocean.”
The study’s authors include representatives from Marine Research Plymouth – a partnership between the University, Plymouth Marine Laboratory (PML) and the Marine Biological Association – who have collaborated over many years to assess changes in Europe’s plankton populations.
They also worked to create the Plankton Lifeform Extraction Tool (PLET), which brings together separate plankton datasets into one central database to give a more accurate picture of the spatial and temporal location of ocean plankton.
Author Dr Angus Atkinson, from Plymouth Marine Laboratory (PML), said: "This study is based on a network of time series from multiple laboratories across the UK and the rest of Europe. It shows worrying declines in some of the key plankton groups, and while the scale of the decline points to large scale climatic warming as the ultimate cause, we still need to understand why some species and regions are changing faster than others."
Author Dr Clare Ostle, Continuous Plankton Recorder (CPR) Research Fellow, added: “One of the key messages here is that warming is impacting the plankton. The trends are showing declines in most areas, however some areas are showing increases in certain plankton groups. This demonstrates the importance of having large-scale coverage when monitoring the plankton and combining with a range of different time-series."
This research has featured in two major reports highlighting in greater detail some of the challenges to the environment being posed by human activities and climate change:
· OSPAR’s Quality Status Report 2023 is the culmination of years of work by over 200 scientists across Europe, detailing the current status of marine biodiversity as well as the specific human activities exerting pressures on the marine environment, with a particular emphasis on climate change. The findings of the report will be used by governments across Europe to inform their marine policy and how they manage human activities to protect our shared marine environment.
· The State of Nature 2023 Report provides a detailed picture of how nature is faring across towns, cities, the countryside and seas. It shows that almost 1,500 species are at risk of UK extinction and there are multiple challenges that need to be addressed to help them. These include a lack of available food, lack of habitat, the impacts of the climate crisis or pollution. It also highlights that, in many cases, the solutions to the challenges nature faces are known with projects to restore habitats such as peatlands, wetlands and woodlands now underway to help capture carbon and save species.