4.1 Assessing impacts of dredging on corals

Description

Information from several major dredging projects was used to describe sediment particle sizes in the water column/seabed, suspended sediment concentrations at different temporal scales during natural and dredging-related turbidity events, and changes in light quantity/quality underneath plumes. These conditions differ considerably from those used in past laboratory studies of the effects of sediments on corals.

The review also discusses other problems associated with using information from past studies for developing thresholds such as the existence of multiple different and inter-connected cause-effect pathways (which can confuse/confound interpretations), the use of sediment proxies, and the reliance on information from sediment traps to justify exposure regimes in sedimentation experiments.

Aims

• To  identify, through a conceptual model, the likely exposure pathway(s) associated with the effects of dredging, including how proximal stressors are interlinked and interact with natural stressors.
• To facilitate a technical understanding of sediments and sediment resuspension, water quality issues associated with dredging programmes, and some of the terminologies used and processes involved.