Assessing the effects of the herbicide diuron on inshore coral (C2.9)

Task leader: Dr Andrew Negri, Australian Institute of Marine Science.

Task associate: Dr David Haynes, Great Barrier Reef Marine Park Authority.

Terrestrial runoff, often containing significant levels of herbicides, such as diuron has been identified as a potentially serious threat to inshore reefs of the GBR (see Williams, 2001). Very little is known of the effects of herbicides on inshore coral species. Diuron is one of the most heavily utilised herbicides for weed control on sugar cane farms and acts by inhibiting photosynthesis in the plants. Diuron is transported from farms to coastal sediments, where it has been detected at levels of up to 10 µg/kg (Haynes et al, 2000a). Most corals rely on photosynthetically active algal symbionts that provide the host with energy. A preliminary study by the applicants, using pulse amplitude modulated fluorometry (PAMF), indicated that diuron has the potential to reduce the photosynthetic efficiency of symbiotic algae in the inshore coral species Acropora formosa at very low concentrations (see Figure attached).

This proposed study will determine the lethal and sub-lethal effects of environmentally relevant concentrations of dissolved and sediment-bound diuron on A. formosa and it’s symbiotic algae in laboratory experiments. Results from this study will assist reef management (GBRMPA) in determining risk to inshore corals from terrestrial runoff containing diuron.