Last updated July 27, 2018 at 3:30 pm
Study reveals impact at a regional scale.
Credit: Rick Stuart-Smith, Reef Life Survey
The mass bleaching across the Great Barrier Reef and Coral Sea in 2016 resulted in rapid, regional scale changes in marine communities.
A new study by researchers from the University of Tasmania shows that fish community structures on southern reefs have become more similar to those in the north and invertebrate communities also changed considerably.
Rick Stuart-Smith and colleagues investigated the ecological changes in corals, algae, fish and mobile invertebrates such as sea urchins by comparing data from surveys of 186 reef sites before the bleaching event (2010 to 2015) and 8-12 months afterwards.
They found that 44 of the sites experienced declines in live coral cover of more than 10 per cent, with the northern Coral Sea reefs suffering the most consistent losses. In addition, declines in coral-eating fish were evident at the most heavily affected reefs.
However, the authors suggest region-wide ecological changes occurred largely independent of coral loss and seemed to be directly linked to sea temperature.
They found evidence of community-wide trophic restructuring, with weakening of pre-existing latitudinal gradients in the diversity of fish, invertebrates and their functional groups. For example, northern reefs saw a decrease in the number of local species of fish whereas there was an increase in the number of small cryptic fish species on southern reefs.
On the basis of their observations, the authors conclude that the recovery process and the scale of the impact remain uncertain. The trajectories of bleached reefs will be greatly influenced by the new community structures that were observed, which are linked to warming-related reshuffling of reef communities.
The paper published in Nature.
