Effects of water quality on the distribution of corals on coastal reefs: development of tools for environmental assessment and risk management (D2.1.1S)

Task leader: Mr Ben Radford, CRC Reef and James Cook University.

Task associate: NA.

Understanding how physical and biological processes interact at different scales to structure coral reef communities has major implications to reef ecology and management. Many different factors have been suggested to determine coral distribution including the population level processes (recruitment, mortality and competition) the prevailing physical environment and episodic events such as crown of thorns, cyclones and bleaching. A number of studies have focused on how coral distribution is shaped by processes and patterns of recruitment, mortality and competition at a number of different spatial scales. In comparison, relatively few quantitative investigations have focused on the contribution of physical factors in structuring reef coral assemblages at different scales.

Levels of turbidity and sedimentation are likely to be important physical factors shaping coral distribution as they affect many physiological functions of corals and can vary greatly between different reef areas. On tropical coral reefs, elevated concentrations of suspended sediment with associated factors such as reduced light are believed to potentially leading to coral stress and reef degradation. Despite this, many inshore coral reefs that can frequently be exposed to high sediment maintain considerable coral diversity and coral cover. These conflicting observations on the impact of sediment on corals may be explained by differences in spatial distribution of species with different sediment tolerance, but at present little is known about how the distribution of coral species varies consistently between different sediment environments.

My PhD focuses on clarifying the relationships between sediment and associated water quality factors on coral species distributions at different spatial scales. I am using GIS and spatial analysis techniques to correlate field data with water quality information while comparing reefs with different sediment regimes. This data is being used in collaboration with current research into coral physiology to developing models of potential coral distribution based on know species distribution and modelled physiological tolerances. This study is applying these models to problems of habitat assessment (using the example of Marine Park planning in the Dampier Archipelago) and impact assessment using the example of assessing the effects of increased sediment associated with marine oil and gas extraction on reefs near the Montebello Islands.