Cold-water coral ecosystems
Spectacular deep-sea cold-water coral reefs several kilometres long are a recent discovery on Europe’s margin. Coral reefs are not restricted to warm, tropical seas but also thrive in the deeper, nutrient-rich high latitude waters where ocean currents prevent sedimentation. The colonial stone corals Lophelia pertusa and Madrepora oculata occur along much of the NW European continental margin and in some Scandinavian fjords. These corals have also recently been discovered in the Mediterranean Sea. Despite intense study in recent years, it is still not known how many coral occurrences there are.
Left: The crab Lithodes maja on a colony of Lophelia with sponge Mycale lingua.
The interplay between coral framework, sedimentation and hydrography has enabled the growth of cold-water coral carbonate mounds along major parts of Europe’s continental margins and deep shelves, some measuring more than 300 m in thickness and several kilometres across. The mounds provide distinct habitats for creatures such as sponges, clams, soft corals and crustaceans.
Right: Sponges Stryphnus ponderosus, Aplysilla sulphureus, Polymastia sp. and Geodia baretti.
Deep-sea coral ecosystems represent true biodiversity hotspots where species richness and diversity rivals that of their tropical cousins. The reefs provide shelter and food to a wide variety of animals, act as nurseries for fishes, represent a ‘cabinet’ for natural medicines and play an important role in absorbing carbon dioxide from the atmosphere. Many of the associated species are of commercial interest and are locally heavily exploited leaving physically damaged and ecologically altered seabed behind. Since the mid-1980s the socio-economic value of cold-water coral ecosystems has risen tremendously. In many areas of the European EEZ, major trawling areas overlap with occurrences of coral ecosystems. This has raised the cold-water coral issue onto the political agenda. OSPAR identified cold-water coral ecosystems as one of the most vulnerable ecosystems where action is required now to mitigate further loss of biodiversity. A proposal to ban bottom-trawl fishing to protect cold-water coral reefs around the Azores, Madeira and Canaries was released by the European Commission in February 2004. Another important step was the EU emergency measure to stop trawling in the Darwin Mound coral province in the Rockall Trough, off NW Scotland.
Cold-water coral ecosystems are important archives of climate oscillations but so far have been poorly exploited for this purpose. Unlike shallow-water tropical reefs, the cold-water corals lived deep enough in the ocean to be unaffected by the massive sea level falls which occurred during glacial periods in the past. Moreover, this type of coral ecosystem thrives in the flow of the intermediate water mass, which provides a unique opportunity to measure mixing processes between the productive surface waters and the deeper ocean environment.
Left: The fish Helicolenus dactylopterus among Lophelia corals.
HERMIONE will address questions relating to the dimensions, distribution and interconnection of deep-sea coral ecosystems along Europe’s Arctic, Atlantic and Mediterranean deep-sea frontier. Emphasis will be given to climate-driven changes, the extent and consequences of human impacts through exploitation of mineral and biological resources at or near coral ecosystems and to understanding ecosystem function. Knowledge will be provided to support stakeholders and policy makers in creating deep-sea governance for sustainable management of resources and conservation of cold-water coral ecosystems.
