Seamounts are usually inactive volcanoes that rise from the bottom of the ocean, but do not reach the surface. Oceanographers define seamounts as an independent feature that measures at least 1000 meters from the seafloor. Although the shape can vary, seamounts are usually cone-shaped. In spite of being invisible from the surface, seamounts can be found in all oceans, usually along the borders of the earth’s tectonic plates and near volcanic hotspots.
Studying seamounts and their features allows geologists to look into the past and study the forces that shaped the world we live in today.
Seamounts push out from the seafloor, thus disturbing the natural flow of currents, causing currents and upwelling where there otherwise wouldn’t be any or a lot less water movement. Because of this, seamounts often have above average abundance of phytoplankton, forming the bottom of complex and diverse food chains. Seamounts provide habitat and spawning grounds for many species that thrive in these conditions.
The abundant marine life on seamounts has also attracted another top predator: humans often armed with destructive methods like bottom trawling and highly sophisticated sonar systems. Bottom trawlers take up everything that gets in their way and most animals do not have the ability to escape, leaving deep, irreparable scars in fragile deep sea ecosystems.
Due to their importance in maintaining biodiversity and sustainable fisheries, more and more seamounts are being protected and carefully managed. In the Azores archipelago, a total of four offshore seamounts are under partial protection, where fishing is allowed and regulated.
Altair and Antialtair
The Seamounts Altair and Antialtair lay far from the Azores archipelago with scarce information available for both seamounts. Altair, to the west of the Mid-Atlantic ridge, is in near pristine condition and thus offers great opportunity for scientific exploration to understand the complex ecosystems seamounts form in the remote locations.
Antialtair, to the east of the Mid-Atlantic ridge, is also very little explored and just like Altair, is expected to concentrate a large number of species and bear unique biological and ecological features.
Sedlo is an isolated seamount located app. 290 kilometres northeast of Graciosa Island. Sedlo sits isolated at 3000 meter depth on the seafloor and rises a majestic 2340 meters to about 660 meters below the surface. Sedlo has a flat top, often an indicator that the seamount has been exposed to great erosion and the top has been grounded down.
To protect the seamount from bottom trawling, gillnets and trammel nets the marine reserve was created. A trawling study found large aggregation of orange roughy (Hoplostethus atlanticus). The orange roughy is an extremely slow growing, large, edible deep-sea fish, that can live up to 150 years. Due to its slow growth, it is especially vulnerable to overfishing and many stocks worldwide are depleted due to overexploitation. Scientists think that Seldo Seamount might be an important breeding ground for the orange roughy. Scientists also found vast amounts of sponges, gorgonians and corals, good indicators of high biodiversity.
Marine Protected Area of the Mid-Atlantic Ridge North of the Azores (MARNA)
The Mid-Atlantic Ridge (MAR) is an underwater mountain chain, almost exactly in the middle of the Atlantic Ocean. It is one of the largest mountain chains in the world; spanning over 16 000 kilometres almost from pole to pole. In the North Atlantic the MAR separates the Eurasian and the North American Plates; in the South Atlantic it separates the African and the South American Plates. As the continents drift apart, new seafloor is formed along the MAR by liquid rock coming out of the Earth’s core. The highest parts of this mountain chain breaks the surface of the Atlantic forming island like the Azores or Iceland.
The MARNA is the largest MPA in Portugal covering an area of more than 93000 square kilometres!