Herbicides in the GBR: Research Overview - Andrew Negri, Stephen Lewis

Herbicides in the GBR: Research Overview - Andrew Negri, Stephen Lewis

Herbicides used to control nuisance weeds on the farm can also be effective once they get into the ocean; even in minute quantities such chemicals have been shown to cause stress to corals, algae, mangroves and seagrass. A little stress has a greater impact than you might think...

Dr Andrew Negri of AIMS presented an overview on the effects of pesticides, particularly herbicides to organisms in the GBR. Pesticides, particularly herbicides from agricultural sources, have been detected all year round near the shore in the GBR. Those called PSII herbicides are of greatest concern and have been found in the highest concentrations in the wet season, at levels known to affect marine organisms. They also remain in the water for a surprisingly long time, some with half-lives of up to 1200 days.

Dr Negri then looked at sensitivity, and found that two seagrass species (Halodule and Zostera) were as sensitive as corals and algae to four commonly used herbicides found in the GBR (Diuron, Atrazine, Hexazinone and Tebuthiuron) and that Diuron could affect photosynthesis at flood plume concentrations.

Herbicides also increase the sensitivity of corals to thermal stress, meaning that as climate change sets in, things could get serious. It is not expected that herbicides alone would pose a threat, but if corals are already stressed by increases in turbidity, sedimentation, increased nutrients and pesticides, the addition of rising temperatures, ocean acidification and changed weather patterns may have severe effects, additive or worse.

These foundation species (i.e. seagrass, mangroves and corals) are highly sensitive to pesticides, and the research suggests that pesticides increase their vulnerability to climate change, leading to the Dr Negri to the conclusion that efforts to significantly reduce pesticide contamination of the GBR should continue. To that end, research users have been engaged, a pesticide working group formed and his results have been incorporated into the risk assessment process for the Reef Plan Scientific Consensus Statement.

BACK to Canberra article

    Publication Type: 
    Research Provider: 
    NERP Focus Area: 


    Search by Project