A black back anemonefish on a bleached anemone. Photo by Dr John Turnbull.
Damselfish and gobies, which usually hide in live coral heads, were now having to hide in dead, algae encrusted coral. Common parrotfish species were there in substantial numbers, suggesting they are benefiting from eating algae on the dead coral.
Sea stars, shell animals and sea urchins were scarce. This was as we feared, as these mobile macroinvertebrates are in widespread decline. If they go, the reef will lose the ecological services which these animals provide, as these organisms recycle nutrients and eat detritus, while some also hunt prey.
From the sky, the Barrier Reef presents as patches and lines of reef, interspersed with a great deal of sand. These sediment and sand communities are not barren. They’re hotspots for crustaceans and worms, feeding grounds for many fish, and the sites where a great deal of nutrient cycling takes place. They are very likely to be hit hard by the heat.
What future can the reef have?
When coral bleaches, it’s easy to tell. It looks very different. But when broader reef ecosystems dwindle, it’s harder. Much of the damage done this summer will take months or even years to manifest.
What will it look like? Research on other reefs is a guide. First, we would expect to see falling numbers of coral-eaters such as butterflyfish. We would then expect to see a drop in coral-dwellers such as the damselfish and gobies living in coral heads.
