If you have ever wondered about the science of the seabed, read on. Dr Sally Campbell's article will help you to better understand the complex ecosystems that sustain the sea from below and will explain why fishing methods (such as dredging and bottom trawling) threaten the very viability of the marine environment as we know it...

Many years ago, as a graduate student, I had the good fortune to spend 3 weeks at Biologische Anstalt, a superb marine research station on Helgoland.  This small island lies at the mouth of the Elbe in north Germany. The research project was to look at different marine deposits, their characteristics, epifauna and infauna. Infaunal species are those animals that live in the sediment, whilst epifaunal species are those that live on the surface of the seabed. Collectively this system is known as the benthos. Many epifaunal species are active and may move considerable distances. For this reason environmental monitoring often targets the infauna, as their presence at a site means that conditions are suitable for them over long periods. Most environmental monitoring uses benthic invertebrates, which include a wide range of polychaete worms, gastropod molluscs, bivalve molluscs, and various crustaceans.