Harnessing plankton dynamics to drive management efforts in the face of rapid environmental change

Plankton, the primary energy resource in marine food webs, respond rapidly to environmental change, making them useful indicators of shifts in ecosystem structure or function. Categorising plankton into groups, or “lifeforms”, can be useful for understanding ecological patterns associated with environmental change. While the marine environment is changing rapidly due to anthropogenic pressures, the relative influence of these pressures across the plankton community remains uncertain, impacting our ability to account for changes in plankton in sustainable marine management. Using methodology developed for the 2023 OSPAR assessment of Pelagic Habitats, we analysed 29 years of Continuous Plankton Recorder data from the North-East Atlantic to examine how temperature, nutrients and background environmental variability impacted abundance. Variability was primarily explained by trends in other lifeforms, indicating shared responses to environmental pressures. Longitude, bathymetry, mixed layer depth, the nitrogen-to‑phosphorus ratio, and temperature were also significant predictors. However, contrasting influences of environmental drivers were detected. For example, small copepod abundance increased in warmer conditions whereas meroplankton, large copepods and fish larvae either decreased or were unchanged. Our findings highlight recent changes in stratification, reflected by variation in mixed layer depth, and imbalanced nutrient ratios are affecting multiple lifeforms, impacting the North-East Atlantic plankton community. To achieve environmental improvements in North-East Atlantic pelagic habitats, it is crucial that we continue to address climate change and reduce nutrient pollution.