Question

During the 19th century, sea otters were hunted almost to the point of extinction. when the number of sea otters became very low, it was noticed that the rich ecosystem of kelp bed forests was also disappearing. it was discovered that the sea otters were predators of sea urchins that were in turn predators of the kelp. when sea otter numbers declined, the sea urchin populations grew, destroying the kelp ecosystem and the many species that depended on it. it was then understood that sea otters were ______ in the ecosystem.

Answer 1

It was then understood that sea otter were a keystone species in the ecosystem. This term refers to a species which seems to be dominant in a biome - once that species is gone, its prey will explode in number, meaning there will be a lot more of them, and a lot less of the keystone species. This, as you can see, happened here in this case.