• Energy Research

Phytoplankton account for approximately 50% of global primary production, form the trophic base of nearly all marine ecosystems, are fundamental in trophic energy transfer and have key roles in climate regulation, carbon sequestration and oxygen production. Boyce et al.1 compiled a chlorophyll index by combining in situ chlorophyll and Secchi disk depth measurements that spanned a more than 100-year time period and showed a decrease in marine phytoplankton biomass of approximately 1% of the global median per year over the past century. Eight decades of data on phytoplankton biomass collected in the North Atlantic by the Continuous Plankton Recorder (CPR) survey2, however, show an increase in an index of chlorophyll (Phytoplankton Colour Index) in both the Northeast and Northwest Atlantic basins3,4,5,6,7 (Fig. 1), and other long-term time series, including the Hawaii Ocean Time-series (HOT)8, the Bermuda Atlantic Time Series (BATS)8 and the California Cooperative Oceanic Fisheries Investigations (CalCOFI)9 also indicate increased phytoplankton biomass over the last 20–50 years. These findings, which were not discussed by Boyce et al.1, are not in accordance with their conclusions and illustrate the importance of using consistent observations when estimating long-term trends.

The EU Marine Strategy Framework Directive (MSFD) requires that Good Environmental Status (GEnS), is achieved for European seas by 2020. These may deviate from GEnS, its 11 Descriptors, targets and baselines, due to endogenic managed pressures (from activities within an area) and externally due to exogenic unmanaged pressures (e.g. climate change). Conceptual models detail the likely or perceived changes expected on marine biodiversity and GEnS Descriptors in the light of climate change. We emphasise that marine management has to accommodate 'shifting baselines' caused by climate change particularly during GEnS monitoring, assessment and management and 'unbounded boundaries' given the migration and dispersal of highly-mobile species. We suggest climate change may prevent GEnS being met, but Member States may rebut legal challenges by claiming that this is outside its control, force majeure or due to 'natural causes' (Article 14 of the MSFD). The analysis is relevant to management of other global seas.

Anthropogenic pressures such as climate change and nutrient pollution are causing rapid changes in the marine environment. The relative influence of drivers of change on the plankton community remains uncertain, and this uncertainty is limiting our understanding of sustainable levels of human pressures. Plankton are the primary energy resource in marine food webs and respond rapidly to environmental changes, representing useful indicators of shifts in ecosystem structure and function. Categorising plankton into broad groups with similar characteristics, known as "lifeforms", can be useful for understanding ecological patterns related to environmental change and for assessing the state of pelagic habitats in accordance with the EU Marine Strategy Framework Directive and the OSPAR Commission, which mandates protection of the North-East Atlantic. We analysed 29 years of Continuous Plankton Recorder data (1993-2021) from the North-East Atlantic to examine how trends in plankton lifeform abundance changed in relation to one another and across gradients of environmental change associated with human pressures. Random forest models predicted between 57 % and 80 % of the variability in lifeform abundance, based on data not used to train the models. Observed variability was mainly explained by trends in other lifeforms, with mainly positively correlated trends, indicating bottom-up control and/or shared responses to environmental variability were prevalent. 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.

AbstractChanges in phytoplankton dynamics influence marine biogeochemical cycles, climate processes, and food webs, with substantial social and economic consequences. Large‐scale estimation of phytoplankton biomass was possible via ocean colour measurements from two remote sensing satellites – the Coastal Zone Colour Scanner (CZCS, 1979–1986) and the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS, 1998–2010). Due to the large gap between the two satellite eras and differences in sensor characteristics, comparison of the absolute values retrieved from the two instruments remains challenging. Using a unique in situ ocean colour dataset that spans more than half a century, the two satellite‐derived chlorophyll‐a (Chl‐a) eras are linked to assess concurrent changes in phytoplankton variability and bloom timing over the Northeast Atlantic Ocean and North Sea. Results from this unique re‐analysis reflect a clear increasing pattern of Chl‐a, a merging of the two seasonal phytoplankton blooms producing a longer growing season and higher seasonal biomass, since the mid‐1980s. The broader climate plays a key role in Chl‐a variability as the ocean colour anomalies parallel the oscillations of the Northern Hemisphere Temperature (NHT) since 1948.

Nature-based Solutions (NbS) have been advocated to protect, sustainably manage, and restore natural or modified ecosystems, simultaneously providing human well-being and biodiversity benefits. The uptake of NbS differs regionally with some countries exhibiting greater uptake than others. The success of NbS also differs regionally with varying environmental conditions and social-ecological processes. In many regions, the body of knowledge, particularly around the efficacy of such efforts, remains fragmented. Having an “inventory” or “tool box” of regionally-trialed methods, outcomes and lessons learnt can improve the evidence base, inform adaptive management, and ultimately support the uptake of NbS. Using Malaysia as a case study, we provide a comprehensive overview of trialed and tested NbS efforts that used nature to address societal challenges in marine and coastal environments (here referring to mangroves, seagrass, coral reefs), and detailed these efforts according to their objectives, as well as their anticipated and actual outcomes. The NbS efforts were categorized according to the IUCN NbS approach typology and mapped to provide a spatial overview of IUCN NbS effort types. A total of 229 NbS efforts were collated, representing various levels of implementation success. From the assessment of these efforts, several key actions were identified as a way forward to enhance the uptake of Nature-based Solutions for informing coastal sustainable development policy and planning. These include increasing education, training, and knowledge sharing; rationalizing cooperation across jurisdictions, laws, and regulations; enhancing environmental monitoring; leveraging on existing policies; enabling collaboration and communication; and implementing sustainable finance instruments. These findings can be used to inform the improved application and uptake of NbS, globally.

Relationships between six calcifying plankton groups and pH are explored in a highly biologically productive and data-rich area of the central North Sea using time-series datasets. The long-term trends show that abundances of foraminiferans, coccolithophores, and echinoderm larvae have risen over the last few decades while the abundances of bivalves and pteropods have declined. Despite good coverage of pH data for the study area there is uncertainty over the quality of this historical dataset; pH appears to have been declining since the mid 1990s but there was no statistical connection between the abundance of the calcifying plankton and the pH trends. If there are any effects of pH on calcifying plankton in the North Sea they appear to be masked by the combined effects of other climatic (e.g. temperature), chemical (nutrient concentrations) and biotic (predation) drivers. Certain calcified plankton have proliferated in the central North Sea, and are tolerant of changes in pH that have occurred since the 1950s but bivalve larvae and pteropods have declined. An improved monitoring programme is required as ocean acidification may be occurring at a rate that will exceed the environmental niches of numerous planktonic taxa, testing their capacities for acclimation and genetic adaptation.

AbstractPhytoplankton primary production is at the base of the marine food web; changes in primary production have direct or indirect effects on higher trophic levels, from zooplankton organisms to marine mammals and seabirds. Here, we present a new time‐series on gross primary production in the North Sea, from 1988 to 2013, estimated using in situ measurements of chlorophyll and underwater light. This shows that recent decades have seen a significant decline in primary production in the North Sea. Moreover, primary production differs in magnitude between six hydrodynamic regions within the North Sea. Sea surface warming and reduced riverine nutrient inputs are found to be likely contributors to the declining levels of primary production. In turn, significant correlations are found between observed changes in primary production and the dynamics of higher trophic levels including (small) copepods and a standardized index of fish recruitment, averaged over seven stocks of high commercial significance in the North Sea. Given positive (bottom‐up) associations between primary production, zooplankton abundance and fish stock recruitment, this study provides strong evidence that if the decline in primary production continues, knock‐on effects upon the productivity of fisheries are to be expected unless these fisheries are managed effectively and cautiously.