Hobday, A.J. and C. L. Hewitt, 2003. Identification of Coastal Zones Using Satellite-Derived Ocean Color and Turbidity: Implications for Ballast Water Exchange Zones, CSIRO Marine Research CRIMP.

Proceedings of the Third International Conference on Marine Bioinvasions, La Jolla, California, March 16-19, 2003, p. 65.

Ballast water is well recognized as a principal vector for the introduction of marine species and management of ballast exchange is receiving increased attention around the world. The water adjacent to the coast (and hence ports) is often referred to as the coastal zone. The coastal zone is a high-risk area for the discharge of ballast water, as many organisms can settle in or arrive at the coast from these waters. Oceanic waters are found beyond the temporally and spatially fluctuating coastal zone. Ballasting activities that occur seaward of the coastal zone are expected to reduce the risk of establishment or transfer of marine pests.  Determining the extent of the coastal zone around a country or port will allow waters suitable for the exchange of ballast water to be identified.

We estimated the boundary between coastal and oceanic water around Australia using historical data from the SeaWiFS satellite sensors. These data comprise (i) color, used as a proxy for chlorophyll a, and (ii) diffuse attenuation coefficient, used as a proxy for turbidity. The coastal zone is high with regard to these variables, and the edge of the coastal zone is identified by declines in the values in an offshore direction for each satellite image. The distances from the coast (and from an example set of 44 Australian ports) are used to compare a range of different probability baselines. The distance of baselines from the coast increases with decreased probability (i.e. lower risk probability baselines are further offshore).

These baselines could be applied to management of ballasting activities for coastal short-duration domestic and to long-duration international shipping; however, in some regions of Australia the baselines are significant distances offshore and in such regions may not provide an effective management solution for coastal shipping.

Contact: Chad Hewitt, Private Bag No 5, CSIRO Marine Research CRIMP, Wembley, Western Australia 6913, Australia
Key Words: Ballast_water, Industry, Prevention
Product Type: Publication, Proceedings
User Type: Boating_and_Shipping