Context-dependency of biodiversity-ecosystem functioning relationships: experimental tests in rocky intertidal communities
Rocky shores comprise a substantial part of the UK’s coastline, and are essential in terms of economic, recreational and cultural value. However, like other important coastal habitats, they are undergoing significant environmental change, threatening the valuable ‘ecosystem services’ that they provide. Human activities such as over harvesting of species and development of coastal defence structures are causing large-scale changes in biodiversity. To add to this, ongoing climate change, including rising sea temperatures and increasing storminess, will drastically alter the conditions under which coastal species interact and ecosystems operate. Understanding how these biological and physical impacts affect the functioning of coastal ecosystems on a small scale, for example, on just a single shore, can give us an idea about what may happen on much larger scales relevant to the management of ecosystem services, which is one of the primary concerns of the CBESS project.
As well as being important in their own right, rocky shores comprise a great experimental system for asking questions about the functioning of (and provision of services by) ecosystems in general. My PhD research at Queen’s University Belfast has examined how changing the diversity of herbivorous species, including limpets and periwinkles, affects algal communities under a range of different environmental conditions, such as increased temperature and wave disturbance. The productivity of algae, largely controlled by these grazing snails, is critical for how rocky shore ecosystems work in this part of the world. I have carried out experiments at different scales, ranging from tanks in an outdoor seawater flow-through system at the Queen’s Marine Laboratory, up to multiple shores of varying wave exposure around the coast of Ireland, testing the effects of diversity change across a wide range of scenarios. Overall, this work has highlighted that, although biodiversity change will remain a critical influence of ecosystem functioning across many scales, including very large ones, it is now essential to find out which physical factors are the most important in modifying its effects. Only then can we predict the consequences of biodiversity loss from coastal ecosystems against a background of global environmental change, and define strategies to sustain the valuable services they provide.