Batfish Increases Reef's Recovery Capacity, Discovery, 12/19/06
By Judy Skatssoon
Source: Discovery News
A fish that gatecrashed an experiment in Australia's Great Barrier Reef has surprised scientists by emerging as an unexpected weapon against the worldwide decline of coral reefs.
Scientists from the Australian Research Council Center of Excellence for Coral Reef Studies (CoECRS) had been studying ways of reversing the effects of coral bleaching at a reef near Orpheus Island in the World Heritage listed marine park.
Part of the research involved generating a bloom of the tropical kelp sargassum weed to mimic the effects of choking invasive weeds and seeing if local weed-eating fish would chomp their way through it, said CoECRS director Professor Terry Hughes.
While herbivorous species like the parrotfish and surgeon fish only nibbled disinterestedly at the algae, the batfish (Platax pinnatus) turned up and cleared the weed within two months.
"The surprising finding ... was that a different group of fish was responsible for reversing the algal bloom," Hughes said.
"Batfish are normally considered to be plankton feeders so we were amazed when we captured on video the effects those fish were having."
Chief investigator Professor David Bellwood of the CoECRS and James Cook University said the batfish's voracious appetite for weed saved the coral from being choked to death.
"In five days they had halved the amount of weed. In eight weeks it was completely gone and the coral was free to grow unhindered," he said.
Bellwood said declining coastal mangroves serve as nurseries for batfish, which are found in reefs around the world.
This highlights the need to preserve mangroves and protect these accidental weed warriors, he said.
Other reef weed-mowers, like the green turtle and dugong, are both seriously endangered, he said.
"If Platax is the last grazer of dense weedy stands on inshore coral reefs and it goes into decline the capacity of these reefs to recover ... could be lost," he said.
Reporting in the journal Current Biology today, Bellwood describes the batfish as a "sleeping functional group," or a species with a hitherto unrecognized role in reef life.
The study is the first extensive demonstration of the role of fish in promoting the recovery of coral reefs, Hughes said.
He said it shows that reefs can adapt to climate change, which has been linked to coral bleaching and subsequent overgrowth of weed.
"We're only beginning to scratch the surface in terms of the changes that climate change is already causing," he said.
"I am of the opinion that coral reefs have already started to adapt ... I think we'll see a shift in the abundance of particular species depending on their ability to respond."