Comparative ecophysiology of the harmful alga Chattonella marina (Raphidophyceae) from South Australian and Japanese waters

The raphidophyte flagellate Chattonella marina was successfully cultured from Boston Bay (South Australia), coincident with mass mortality of farmed bluefin tuna (Thunnus maccoyii) in April 1996. Grown under laboratory conditions at 150 μmol m-2 s-1 irradiance, optimal growth (>0.5 day-1) occurred at a temperature of 25°C and a salinity of 30 p.s.u., but good growth (>0.3 day-1) also occurred between a temperature of 10 and 30°C and at a salinity of 15-45 p.s.u. However, cultures grew much faster at an irradiance of 450 μmol m-2 s-1 (1.08 day-1). While Australian C.marina had similar temperature and salinity requirements as well-studied Japanese cultures from the Seto Inland Sea, the Australian strains exhibited a light saturation level for growth four times higher than that reported from Japan (150 μmol m-2 s-1). An adaptation to higher light intensities was reflected in higher concentrations of microsporine-like amino acids in the Australian strains. The different light adaptation phenotypes were still apparent after long-term culturing under similar physiological conditions. Potential growth habitats for this ichthyotoxic flagellate in the Australian region and implications for finfish aquaculture industries are discussed.