Implications of parental diuron exposure for coral reproduction and larval metamorphosis

Neal E. Cantin, MSc student, James Cook University and Australian Institute of Marine Science

Herbicides are widely used within catchments adjacent to the Great Barrier Reef Marine Park by the sugarcane and tropical fruit industries. In Queensland approximately 197 tonnes of the herbicide diuron are applied annually by the sugarcane industry alone, and high concentrations have been detected in riverine water samples and in marine sediments.

Most corals rely on symbiotic algae called zooxanthellae for additional energy obtained from photosynthesis. This energy is used for daily cell maintenance, growth and reproduction. Diuron inhibits photosynthesis in zooxanthellae.

In this study the implications of diuron-induced photosynthetic stress will be studied to determine the impacts of herbicides on the reproductive processes of reef-building corals. Producing gametes, fertilisation and embryo formation are among the most sensitive developmental stages in the life history of organisms.

Broadcast spawning and internal brooding nearshore coral species (Acropora tenuis and Pocillopora damiconris, respectively) will be used to compare the effects of parental diuron exposure on late stage reproductive development and the competency of the resultant offspring for recruitment. These results will provide strategic advice for the Great Barrier Reef Marine Park Authority and catchment managers regarding threshold concentrations of herbicides from agriculture that may impact on coral reproduction.