Fish will play a vital role in helping Australia’s Great Barrier Reef cope with the ravages of climate change.
That’s the conclusion of a major scientific paper published today in the international journal Current Biology.
Experimental cages excluded herbivorous fishes for the 3-year experiment
A dramatic experiment run by an international team of researchers from the ARC Centre of Excellence for Coral Reef Studies (CoECRS) has shown that a healthy fish population is essential for coral recovery after a severe bleaching event, storm or disease outbreak.
“The combined effects of overfishing, pollution and climate change are seriously damaging coral reefs around the world and causing their replacement by weedy growth,” team leader Professor Terry Hughes said.
“We followed the recovery of corals that had been severely damaged by bleaching. The corals were on a reef where fish populations were unusually intact due to the Great Barrier Reef Marine Park Authority’s no-take policy.”
“We also fenced the fish out of some areas, and compared coral recovery with and without lots of fish.”
“The result was dramatic. The coral cover virtually doubled where the fish had access, while the fenced-off areas became overgrown with slimy weed and the corals failed to recover.”
The team concluded that having intact fish populations will be vital to successfully managing the resilience of tropical coral reefs from the impacts of climate change and human activity. The importance of this result is accentuated by the findings of the latest report of the Intergovernmental Panel on Climate Change (IPCC).
“We can’t prevent future bleaching except though international action on greenhouse gas emissions,” said co-author Professor Ove Hoegh-Guldberg. “In the meantime, it’s important to do whatever we can to minimize the damage and assist reefs through these difficult times.”
“The larger herbivorous fishes – such as parrot fish and surgeon fish – are particularly important in keeping recovering corals free from weedy overgrowth,” Professor Dave Bellwood said. “This research indicates it is important to avoid overfishing of these herbivores at all costs.”
Coral reefs provide vital economic, social and cultural services to many societies around the world that depend on them. In Australia alone the Great Barrier Reef is valued at over $5 billion a year, employs 68,000 people and is a celebrated cultural icon.
“For reefs to withstand the rigours of climate change, they need to be resilient – able to bounce back after a severe shock such as a bleaching episode, an outbreak of disease or a hurricane,” Senior Research Fellow Morgan Pratchett said. “That means maintaining the richness and diversity of their assemblages of coral, fish and other animals.”
A sixth of all the world’s corals were hit during a recent major heating event (1998-99), pointing to the potential scale of climate impacts. In many areas already affected by human activity such as pollution and overfishing, they have not yet recovered.
“As the world continues to warm, it’s only a matter of time before the next major bleaching event occurs. Once corals are replaced by weed – known as a phase shift – it is extraordinarily difficult, if not impossible, to bring them back again,” Prof Hughes said.
“This experiment shows that one way to prevent a phase shift from taking place is to have an intact population of herbivores ready to pounce on any weeds that may sprout before the corals can regenerate,” Prof Bellwood said.
“Herbivorous fish are rarely caught by professional fishermen in Australia – though they are still hunted by spear fishers – but around the world they are under remorseless pressure. Over time this could lead to the permanent loss of huge swathes of coral reef with serious consequences for communities which depend on them.”
Fellow author and Research and Monitoring Manager with the Great Barrier Reef Marine Park Authority, Dr Laurence McCook, said the research provided valuable information for the protection of the Great Barrier Reef.
Dr McCook, who was recently awarded a prestigious Pew Fellowship in Marine Conservation for his work on resilience and climate change, said this study showed that no-take areas such as those applied on the Great Barrier Reef in the Green Zones made important contributions to the Reef’s resilience.
“Maintaining resilience is a vital aspect of reef management,” he said.
“A priority for the Great Barrier Reef Marine Park Authority is to build the Reef’s resilience through initiatives such as no take zoning and reducing water pollution.”
Professor David Bellwood, CoECRS and James Cook University, +61 7 4781 4447 mob +61 0419 422 815
Professor Ove Hoegh-Guldberg, CoECRS and University of Queensland, +61 7 3365 1156 or +61 0401 106 604
Dr Laurence McCook, Great Barrier Reef Marine Park Authority, +61 7 4750-0787 or +61 0408 804 765 or firstname.lastname@example.org
Professor Terry Hughes, CoECRS, James Cook University, +61 7 4781 4000 or email@example.com
Jenny Lappin, CoECRS, +61 7 4781 4222
Jim O’Brien, James Cook University Media Office,+61 77 4781 4822
Dr Robert S. Steneck, University of Maine, +1 07 563 3146 ext 233; or firstname.lastname@example.org
Paper details: “Phase Shifts, Herbivory, and the Resilience of Coral Reefs to Climate Change”, Current Biology 17, February 20, 2007. Link to full text or pdf