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Marine Ecosystems

Programme background

The diversity of life in marine ecosystems is exceptional; while only one animal phylum is exclusively terrestrial, 21 phyla are marine endemics.

The functional roles of this marine biodiversity underpin major ecosystem services. These include food production, climate regulation through the cycling of carbon and other macronutrients, and a range of cultural values (for example recreation and tourism) that rely on the natural environment to a far greater extent than on land.

Biodiversity in marine ecosystems is experiencing ongoing environmental change: ecosystem restructuring generated by fisheries; eutrophication, pollution and other environmental degradation; climate-driven changes and growing human consumption and pressures, such as the recent expansion of the marine renewable energy sector.

Understanding the consequences of these changes, and designing, testing and refining potential management solutions to address them, is clearly important for the long-term delivery of services from marine ecosystems.

Marine food webs play a key role in regulating these ecosystem services, but there are important gaps in our understanding of species' functional roles and the way they might respond to environmental change.

First, although there is evidence that marine food webs are affected by both 'bottom-up' processes (such as biophysical factors affecting primary productivity) and 'top down' ones (for example, top predators modifying the biomass of lower trophic levels), existing knowledge is much greater for lower trophic levels and associated biophysical factors.

This means it is currently difficult to understand the relative roles of these processes, and hence the extent to which environmental change cascades through marine food webs and affects ecosystem services.

Second, these 'bottom up' and 'top down' processes are inherently dependent on scale. For example, small-scale changes in seabed topography, waves and currents can produce 'hotspots' of primary productivity that then affect the spatial distribution and abundance of higher trophic levels; large-scale removal of top predators through fishing or other activities can have a range of impacts across scales.

Scale-dependence is poorly understood, however, making it difficult to quantify the large-scale impacts on ecosystem services of changes at small spatial scales (such as marine conservation zones), and vice versa.

Third, it is unclear how functional diversity affects the way marine food webs regulate ecosystem services. This is potentially important because there is growing evidence that the loss of biodiversity from marine ecosystems can harm ecosystem functioning and services.

Improving our understanding in these three areas would facilitate the development of more realistic marine ecosystem models, which in turn would provide important tools for exploring the impacts of environmental change on marine ecosystems, and testing potential management solutions.

This action has been designed to address the knowledge gaps outlined above. It has three main goals:

1. Improve our understanding of how key ecosystem services such as food production, macronutrient cycling and cultural values by marine food webs are affected by the relative roles of 'top down' and 'bottom up' processes, scale-dependence in these processes and functional diversity at different trophic levels.
    
2. Integrate the improved knowledge and understanding gained in goal 1 with existing ecosystem models to explore the impact of environmental change on the structure, function and services associated with marine food webs across scales.
    
3. Apply the models developed in goal 2 to test the impact of potential management solutions, such as marine conservation zones, on the structure and function of marine food webs across scales, and explore the efficacy of specific indicators of good environmental status.

These goals will be addressed through an integrated project in the Northeast Atlantic.

For further information, including scientific references, please see the Marine Ecosystems theme action plan document available on the resources page.