By Christine Flatley

Source: Herald Sun

02/05/07 

Pesticide run-offs are putting Australia's already fragile coral reefs at greater risk of destruction, a new scientific study has shown.

The study, published in the Marine Ecology Progress Series journal, shows corals on the Great Barrier Reef are being harmed by agricultural chemicals, even when the chemicals are only present in small quantities.

Scientists from the Australian Institute of Marine Science (AIMS), the ARC Centre of Excellence for Reef Studies (ARC CoE) and James Cook University say pesticides are so poisonous that they can prevent coral spawning, and consequently the reef's ability to regenerate and protect itself.

The corals most at risk, the study found, were those in their infancy.

"Previous studies have focused only on the adults, which seem more robust to insecticides," AIMS scientist Dr Andrew Negri said.

"Our study looked at the fertilisation, larval development, survival and metamorphosis and we found that some of these stages were very vulnerable to these chemicals at very low concentrations."

The study found coral settlement – a crucial development stage – was reduced by between 50 and 100 per cent following 18 hours exposure to very low concentrations of pesticides.

The agricultural fungicide MEMC (methoxy-ethyl-mercury chloride), which is regularly used on sugarcane crops, was found to be particularly aggressive.

Tiny concentrations of MEMC were found to not only affect vulnerable baby coral but to cause bleaching in adult corals in tiny concentrations.

The researchers have suggested current water quality guidelines for the reef may not be sufficient to adequately protect all coral life stages.

They have warned that chemicals combined with rising sea temperatures caused by global warming may result in the destruction of the Great Barrier Reef.

The Great Barrier Reef Marine Park Authority is currently overseeing the implementation of the 10-year $40 million Reef Water Quality Protection Plan to improve land management practices in the catchment area.