As if threats from coral bleaching and acidifying oceans were not enough to coral reefs, Australian scientists have identified one more threatening the Great Barrier Reef: herbicides.
A four-year study by Stephen Lewis and coauthors has found herbicide residues in rivers and creeks and in marine waters within the Great Barrier Reef lagoon.
From 2005 to 2008, the scientists analysed 600 water samples for pesticide concentrations from 76 river and creek sites in three geographical regions (representing 35%) of the Great Barrier Reef catchment area: the Tully"Murray, Burdekin"Townsville and Mackay Whitsunday regions.
The authors found a suite of herbicides, including diuron, atrazine, ametryn, hexazinone and tebuthiuron, commonly detected in the waterways studied, with the chief culprits appearing to be sugar cane fields and grazing land.
The authors predict, the mixture of herbicide residues following river discharge events has the capacity to produce cumulative chronic effects on sensitive species of marine plants and corals. These effects may cause a change in the community structure of mangrove, seagrass and coral reef ecosystems.
The study is to be published in an upcoming issue of the journal Environmental Pollution.
For more information, see the paper: Lewis, SE, JE Brodie, ZT Bainbridge, KW Rohde, AM Davis, BL Masters, M Maughan, MJ Devlin, JF Mueller and B Schaffelke (2009) Herbicides: A new threat to the Great Barrier Reef. Environmental Pollution, doi:10.1016/j.envpol.2009.03.006.