Another hypothesized human-related cause is fertilizer runoff.
People use fertilizer for their crops and plants and a lot of it eventually makes its way from land into the seas.
It's fertilizer, so it has a lot of nutrients.
These nutrients have an effect on the starfish, because they cause an increase in the growth of phytoplankton.
Phytoplankton are microscopic plants that grow in the ocean.
Larval CoT starfish eat phytoplankton in their first month of life, so more fertilizer in the ocean means more phytoplankton, which means more starfish, bad for the reefs.
Now, the final hypothesis has to do with storm events.
If some reefs are destroyed by storms, starfish populations that inhabited those reefs would have to condense and concentrate on the reefs that are left.
So this can cause a kind of mass feeding frenzy.
So we have ideas, but no real answer.
And because we aren't sure of the causes for starfish population increases, it's difficult to prevent them.
I mean, some progress has been made.
For example, new survey techniques have enabled us to detect population increases when the starfish are quite young, so we can be ready for them.
But meaningful progress requires much better evidence about the cause.
On the bright side, in all the research being done on causes, we have discovered something related to how starfish populations might affect coral reef diversity.
We think that when reefs are damaged, after a few years, the fastest-growing corals repopulate the areas.
And these fast-growing species can grow over the slower-growing species of coral, denying them light and preventing them from recovery.
However, the faster-growing species are the preferred food of the CoT starfish.
So when an outbreak of CoT starfish occurs, they thin out the fast-growing coral and may give the slower ones a chance to reestablish.
So without the outbreak, the diversity of coral would be reduced.