SEAMOUNTS
Seamounts are undersea mountains, rising from abyssal depths, usually formed by volcanic activity. Unlike islands, they don’t reach the surface and unlike plateaus they usually have a conical shape. Seamounts form stepping stones in the ocean for animal dispersal and have often been described as oases of abundance and biomass in the ocean. They provide important habitats for open ocean animals, deep-sea fish and invertebrates that thrive on the elevated position of the seabed. They provide a solid surface, something hard to find in the open ocean, for a diverse range of animals including corals, sponges, and other filter feeding animals which attach themselves in dense colonies to the seamount slopes. The open ocean above the summits and sides of seamounts are also unique, and show unique biological or biogeochemical properties. Currents well up and swirl around the mountain, serving up a constant supply of nutrients and plankton, a phenomenon referred to as the “seamount effect”.
Pressures on seamount ecosystems include benthic and pelagic fisheries, petroleum exploration and in some areas, seabed mining. Seamounts support vulnerable slow growing animals that are increasingly threatened by fishing and mining, so seamount ecosystems need protection. Seamount fishes such as the orange roughy are especially vulnerable to fishing because these long lived species gather in large shoals that can be targeted by high-technology fisheries that can deplete this resource from large areas. Coral dominated seamount ecosystems are not very resilient to disturbance by bottom trawling, because there are limited alternative habitats capable of supporting associated species, and because trawling typically removes entire coral habitats from large areas of individual seamounts.
Management of seamount ecosystems needs to account for changing oceanographic conditions (ocean acidification), as well as the direct impacts of human activities such as bottom trawling and mining.
Proposed MPAs that include seamounts are Southeast Atlantic Seamounts that includes Protea, Argentina and an unnamed seamount, and the Southwest Indian Seamounts that includes Natal Seamount.
