About This Project

Coastal ecosystems are sensitive to human-induced pressure from fisheries and pollution that lead to localized extinctions of specific organisms. These extinctions disproportionately affect larger, predatory animals (megafauna), with cascading effects upon ecosystem-scale carbon cycling pathways. This project will test how selective removal of larger predatory organisms alters ecosystem structure and function, changing energy flow and carbon cycling pathways in coastal sediments.

Ask the Scientists

What is the context of this research?

Coastal sediments account for around 5% of the global sea floor but are responsible for 50% of sea floor carbon cycling. Coastal regions are under pressure from fisheries and climate change leading to species loss and changes in how ecosystems function. At the sea floor, species loss most acutely affects larger predatory animals (megafauna) that directly control the structure of animal communities with cascading impacts upon the smaller animals (macrofauna) and microorganisms at the seafloor. The patchy spatial distribution of megafauna, however, means they are often excluded from studies of seafloor ecosystem functioning. Accurately predicting global-scale impacts of marine species loss requires an understanding of species loss effects on fundamental ecosystem processes.

What is the significance of this project?

At present, the effects of marine predator loss upon ecosystem functioning in soft sediments is poorly understood. Coastal sediment ecosystems are important components of marine nutrient cycling where fishery-induced predator loss is an acute problem. This would be the first study to quantify how changes in predator abundance affect sediment ecosystem structure and carbon recycling and burial rates, under both present and future climate regimes. Marine predators such as crabs and lobsters represent high value fisheries but play a vital role in controlling sea bed ecosystem functioning. This project will provide critical information regarding the environmental impact of fisheries and how this can be managed under a changing climate.

What are the goals of the project?

Using our research aquarium as a mesocosm, I will experimentally alter abundances of the green crab (Carcinus maenas) from natural levels down to extinction to test how this affects ecosystem structure. I will investigate changes in animal community (which species do well, which do badly), and carbon recycling rates. Carbon dioxide is absorbed by microscopic algae at the sediment surface and converted to biomass. Algal biomass can then be consumed by the animals and recycled to carbon dioxide, or buried and preserved within the seabed. The green crab is a model species both as a target for fisheries in Europe, and as an invasive species in the coastal habitats of America, Africa and Australia. These experiments will be performed under current (ambient) and future (warming) climate regimes.