WAMSI 2 - Dredging Node - Project 9.1 - Effects of dredging related pressures on critical ecological processes for other organisms

Brief description

Dredging is a common activity used for the development of marine infrastructure. It involves the physical removal of sediment from a dredged area in order to increase depth to allow for shipping, the laying of underwater pipelines and other port related developments. Dredging has significant effects on the marine environment, particularly the benthos, with direct and indirect impacts on marine flora and fauna. It is the key goal of dredging operations to reduce all potential impacts of dredging to acceptable levels. Two workshops were held: First from 29th – 30th November 2013 at CSIRO Floreat and the second from 22nd - 23rd September 2014 at CSIRO Floreat. The objectives of Workshops I & II were as follows: * identify the timing of critical ecological processes in tropical and temperate ecosystems with a focus on non-coral and non-fish biota (seagrasses, seaweeds, sponges, ascidians, bryozoans, molluscs, echinoderms, crustaceans and non-coral cnidarians); * identify environmental windows for critical ecological processes identified in Objective 1. This will be achieved by compiling information on the timing of reproduction, release of propagules and recruitment for these organisms, as well as the temporal and spatial scales of reproduction and recruitment events; * identify potentially critical periods (environmental windows) and locations when mitigating scheduling and processes could be employed to reduce the impact of dredging on non-coral and non-fish biota; * review the state of knowledge regarding potential effects of dredge-related sediments and other dredge-related pressures on these key ecological processes; and * identify the potential for invasive species to become established. The data product for this project is final report (.pdf).

Lineage

Statement: Vulnerability to dredging was assessed for life history characteristics (LHCs) on a taxon-specific basis. For the invertebrates, six key LHCs were identified and used to predict vulnerability to dredging. These included: feeding strategy, mobility, life span, reproductive strategy, reproductive season and developmental strategy. A vulnerability index (VI) was then developed in order to assign a vulnerability score to each ecologically important taxon based on its particular LHCs. For the seagrasses and the macroalgae, sensitive periods in the life histories were identified and their response to decreases in light, burial and sedimentation was reviewed. Vulnerability to dredging was then predicted for major genera