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Seamounts

Ecology

Seamounts swarm with sea life surrounded by the sea floor containing little life in comparison. Food resources carried by passing currents maintain the complex ecosytems of seamounts. Current speeds around seamounts are greatly increased as the relatively slow deepwater currents are forced to pass around these obstructions meaning that there are more plankton in the area so more organisms can live there.

The Cold-water corals, sponges, sea anemones, and sea fans form crowded communities that consume mostly plankton drifting along near the bottom.Through this “jungle” move starfish, tiny lobsters, fish, and worms and other animals The unique field of 70 seamounts is home to a host of corals and creatures as diverse as the Great Barrier Reef only they are 1000 metres below the surface! Each seamount has its own unique and diverse ecosystem.

Seamounts provide habitats and spawning grounds for larger animals, especially fish. Marine mammals, sharks, tuna, and cephalopods all gather over seamounts to feed, as well as some species of seabirds when the seamounts are shallow. The volcanic rocks on the slopes of seamounts contain large populations of suspension feeders, especially corals.

As well soft sediments tend to build up on seamounts allowing large numbers of annelid marine worms, oligochaete worms and gastropod molluscs. Marine protozoans have also been found. They tend to gather small particles and forming beds, which alters sediment deposition and creates a habitat for smaller animals. Many seamounts also have hydrothermal vent communities and many may be important stopping points for some migratory animals, especially whales.

Researchers found around 300 species of invertebrates and fish and between about 25% and 50% of these species were new discoveries.

Corals, soft seapens, sponges and seawhips attach themselves to the hard surfaces to form amazing underwater forests on the seamounts. Sea spiders crawl through these forests, while slipper lobsters make homes in burrows amongst the rock and coral. Large numbers of worms and small crustaceans live in the soft sediment.

Orange Roughy and deepwater oreos swim continuously around seamounts to avoid being swept away by strong currents. Deeper down, bizarre eel-like and blob-like fish can be found.

Threats

The greatest natural danger is flank collapse caused by lava from under the surface which can be slowly pushed up from deep within the earth into any cracks or spaces it can find.
Commercial trawl fishing presnets the biggest pressure. It causes destruction of seamount animals like corals, sea pens and sponges and over-fishing of sensitive fish stocks, such as the Orange Roughy. Nearly 80 species of fish and shellfish are commercially harvested from seamounts.

Once depleted, sea mount species require decades, if not centuries, to recover. In fact, on some sea mounts in other parts of the world, commercial fish species have been wiped out. To make sure that the sea mounts stay around into the next century, they need to be protected in marine parks and reserves, and the threats affecting them need to be stopped.

 


Warty oroe (Allocyttus verrucosus)
Found in all southern oceans at depths of between
300 and 1,600 m. Its length is up to 42 cm.
Warty oreos live in the waters of continental slopes, and they form in large schools over rough terrain.
They are very long living creatures, the oldest
living to be 140 years old.


Deep sea coral


Serpent star on black coral


Plankton (highly magnified)

   

Next: Some unusual animals   ...

 

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