Jobs, livelihoods and ecotourism industries can benefit from having a diverse supply of weed-eating fish on the world's coral reefs, marine researchers say.
Despite their small size, relative to the sharks, whales, and turtles that often get more attention, herbivorous fish play a vital role in maintaining the health of coral reefs, which support the livelihoods of 500 million people worldwide, say researchers from the ARC Centre of Excellence for Coral Reef Studies at James Cook University, and the Australian Institute of Marine Science.
"Herbivorous fishes protect coral reefs by limiting the growth of algae, or seaweed," says Loc Thibaut, lead researcher of a new study that has been published in the journal Ecology. "Seaweeds grow rapidly and compete with corals for space. If left unchecked, they can smother the corals and take over the reefs. This shift, once it happens, is extremely difficult to reverse."
The study shows that having high biodiversity of herbivorous fishes provides strong "insurance" for coral reefs. A diverse set of herbivores ensures that seaweeds are kept under control, because when some species take a hit and decline, others increase to fill the gap. This makes seaweed control more stable over time, something researchers call the "portfolio effect".
"It's like having a diverse stock portfolio you wouldn't put all your money into one particular stock, because if that company goes down, so will your life savings," says Professor Sean Connolly, a Chief Investigator at the Centre. "A very similar principle works in ecosystems."
An example of the disastrous effects of having only one herbivore as 'gatekeeper' is the extensive coral loss in the Caribbean in the 1980s.
"In the 80s, overfishing left a species of sea urchin as the only animal controlling seaweed growth on Caribbean reefs. When a disease broke out, the sea urchin population collapsed - and there was nothing to keep th
|Contact: Sean Connolly|
ARC Centre of Excellence in Coral Reef Studies