Damn damsels

Until the 1980s, staghorn corals (Acropora sp.) were a dominant member of Caribbean coral reefs. They were hit hard by a variety of diseases, hurricanes, and anthropenic impacts. So hard that they're now endangered. There's been an unforeseen complication. The three-spot damselfish, Stegastes planifrons, kill portions of coral to culture algae and provide hiding spots. They're aggressive, and defend their gardens ferociously. When staghorn corals were abundant, the damselfish preferred to set up housekeeping among their branches, and the relatively fast-growing staghorns could stay ahead of the damage caused by the fish. In the absence of staghorns, damselfish have taken to slower-growing head corals, and they are wreaking havoc on the already stressed corals.

The impact of the damselfish has been recognized for some time, although it was believed that their increase in abundance and impact was the result of a release from predation resulting from overfishing of large fish like groupers. A new paper appearing in PLoS One identifies the changing nature of Caribbean coral reefs as the root of the problem.