Like land mounts, seamounts are created by shifting tectonic plates. Most are old and eroded. They harbor a stunning variety of shapes, both on their scraggly surface and in the sea life they support. They constitute a rich ecosystem with over a thousand species. Some are unique to it. Some are even specific to a particular seamount. Species also vary by depth.
This variety is made possible by the nutrient richness the seascape provides : The vertical mount, sitting on a horizontal ocean floor, disrupts underwater currents, tides and waves, causing turbulence, thus concentrating the incoming nutrients, and stirring the sediment foraging fish feed on. Small creatures feed the larger ones, and so on to the aquatic megafauna. Seamounts especially attract sharks, where they stay for days at a time.
Sharks hover around seamount edges in large amounts, rather than over the summit. The overfishing of small fish has depleted sharks' food supply, so overfished areas are detectable from their conspicuous lack of sharks. Scientists hope shark patterns can help the enforcement of the no-fishing laws protecting the seamounts.
Deep-sea mining and debris left behind by overfishing constitute another threat to the marine ecosystems. Yet, only one to two percent of seamounts are protected, in spite of scientists' efforts. This ecosystem of varied, fragile, long-lived, slow-growing, or still undiscovered smaller species can recover from damage when protected, as shown by some seamounts left undisturbed for decades. Unfortunately, seamounts's great beauty is increasingly threatened.