Understanding biological checks and balances

Published: 15 October 2015

At Queen’s University Belfast we have been running experiments and conducting surveys to better understand biological checks and balances. To further our understanding of the determinants of ecosystem stability within marine ecosystems, we have been running two separate experiments at the large mesocosm facility at Queen’s Marine lab.

The first set of experiments looks at how the feeding rate of predators is dependent on both body size and abundance of prey. Generalizations on the relationship between these variables can then be fed into mathematical models to determine how lose or addition of predators can alter marine ecosystems. To date, the focus has been on predators such as starfish and crabs, but we will soon begin studying larger predators such as dogfish and rays.

The second experiment we conducted altered the presence of predators (crabs or amphipods), fast growing macroalgae, and detritus (dried kelp) to quantify which of these variables is most important for the stability of food webs and the production of animal biomass which is important for higher trophic levels that often end up on people’s dinner plates.

Initial results suggest that dried kelp may be of similar importance to food web dynamics as other food web components. This experiment is particularly noteworthy because one of the MERP goals is to determine the fate of dislodged kelp and its importance for other ecosystems, considering up to 80% of kelp production is exported out of kelp forests.

Additionally, we organized the Northern Ireland section of a survey being conducted throughout the Irish Sea, that has and will continue to measure the relative contribution of kelp to benthic communities from the intertidal zone to 20 km off shore. Multiple sampling techniques are used to catch many species from small worms inside the mud to large fish and crabs. The tissue of the animals can then be analysed to see what part of their diet originates with kelp and what part comes from plankton.