TRANSPORT OF TOXIC DINOFLAGELLATES VIA SHIPS BALLAST WATER - BIOECONOMIC RISK ASSESSMENT AND EFFICACY OF POSSIBLE BALLAST WATER MANAGEMENT STRATEGIES

The results of 10 yr of Australian research efforts on transport of to xic dinoflagellate cysts via ships' ballast water are reviewed, supple mented with the conclusions of similar studies now underway in Europe, Israel, North America, Canada, Japan, China and New Zealand. Toxic di noflagellates are probably the best studied model organism to assess t he bioeconomic risks of ballast water introduction of nonindigenous ma rine pests. A plausible scenario for their successful introduction and establishment in Australian waters is: (1) ballast water intake durin g seasonal plankton blooms and to a lesser extent via resuspended cyst s in sediments from Japanese or Korean ports; (2) survival as resistan t resting cysts during the ballasting process, the voyage in a dark ba llast tank, and subsequent ballast water discharge (inoculation); (3) successful germination of cysts, sustained growth and reproduction of plankton cells in an Australian port; and (4) further spreading via co astal currents or domestic shipping, culminating under suitable enviro nmental conditions in harmful algal blooms impacting on aquacultural o perations (causative organisms of paralytic shellfish poisoning). Unti l international agreement and acceptance of a fully effective, practic able, safe, economically viable and environmentally friendly ballast w ater treatment is achieved (mid-ocean ballast water exchange and heat treatment are the only options offering promise at present), an intern ational warning network for algal blooms in ports appears to be an eff ective way to minimise risks. It is also recommended that aquaculture operations and marine parks should be sited well clear of the ballast water influence of shipping ports.