Mussels Decline: Water Quality Suffers
Queen’s University, Ireland, has joined a project to try and save the horse mussel reefs off the Irish coast.
The horse mussel is an important biological tool because it ‘engineers’ water quality by filtering the water to obtain food, and is also an indicator of biological diversity because many other marine species rely on this bio-engineering behaviour for their own survival. The mussels, provide a vital stabilising effect that binds the seabed by linking living mussels, dead mussel shells and sedimentary deposits.
Mussels unite - marine life thrives
Because the mussel is a filter feeder, it also provides a flux of organic material as a food source for other species such as sponges, soft corals, anemones, tubeworms, brittlestars, urchins, starfish, barnacles, crabs, spider crabs, whelks and other gastropods, scallops and fish, as well as offering anchorage points for seaweeds. All this means that the mussel reefs become an extremely rich habitat. But the action of trawlers over the reefs, which are often exposed at low tides, has seriously damaged the beds in the past.
It was discovered that the reefs were in serious decline in 2004 and a new inter-agency approach has been launched to try and save them. A (temporary) fishing ban has been in place in the Strangford Lough since late 2003, as one cause of the decline but the horse mussel reef communities appear to still be declining rapidly.
Commercial concerns drive new approach
Under EU law, the Strangford Lough is classed as a conservation area, meaning that the UK government is required by law to protect all its marine species. However, it seems likely that increased commercial concern driven by the realisation that the mussel beds serve as a nursery for many species of commercial importance to fisheries such as scallops and crabs, has driven this new initiative.
The action of mussels on water quality is profound – blue mussel reefs, for example, are able to filter an amount of water sufficient to fill the Albert Dock in just two days.
Queen’s University has previously worked on the restoration of the European native oyster and freshwater pearl mussels and its initial survey has discovered that the mussel density is less than 25% of what would be considered ‘good’. As an initial intervention, the university is raising the mussels in intensive culture in marine laboratories in Portaferry in order to build stocks for reintroduction.
Strangford Lough courtesy of ahisgett at Flickr under a creative commons licence
