Judith-Anne Marshall

Ichthyotoxicity of Chattonella marina (Raphidophyceae) to damselfish ( Acanthochromis polycanthus ): the synergistic role of reactive oxygen species and free fatty acids

This investigation aimed to elucidate the relative roles of putative brevetoxins, reactive oxygen species and free fatty acids as the toxic principle of the raphidophyte Chattonella marina, using damselfish as the bioassay. Our investigations on Australian C. marina demonstrated an absence or only very low concentrations of brevetoxin-like compounds by radio-receptor binding assay and liquid chromatography-mass spectroscopy techniques. Chattonella is unique in its ability to produce levels of reactive oxygen species 100 times higher than most other algal species. However, high levels of superoxide on their own were found not to cause fish mortalities. Lipid analysis revealed this raphidophyte to contain high concentrations of the polyunsaturated fatty acid eicosapentaenoic acid (EPA; 18-23% of fatty acids), which has demonstrated toxic properties to marine organisms. Using damselfish as a model organism, we demonstrated that the free fatty acid (FFA) form of EPA produced a mortality and fish behavioural response similar to fish exposed to C. marina cells. This effect was not apparent when fish were exposed to other lipid fractions including a triglyceride containing fish oil, docosahexaenoate-enriched ethyl ester, or pure brevetoxin standards. The presence of superoxide together with low concentrations of EPA accelerated fish mortality rate threefold. We conclude that the enhancement of ichthyotoxicity of EPA in the presence of superoxide can account for the high C. marina fish killing potential

Chemotaxonomic survey of sterols and fatty acids in six marine raphidophyte algae

Fatty acid and sterol profiles allowed for clear discrimination betweentheraphidophyte genera Chattonella,Heterosigma, Fibrocapsa andOlisthodiscus, but exhibited little differentiation forindividual Chattonella species(C.marina, C. antiqua and C.subsalsa). Sterol and fatty acid profiles do not support theseparation of Chattonella antiqua and C.marina as distinct species. Ecophenotypic variations in lipidprofiles were also observed between Chattonella strainsfromdifferent geographic locations. Sterol signatures which may be useful aschemotaxonomic markers were: the absence of C27 sterols (cholesteroland 24-dihydrozymosterol) in Heterosigma akashiwo; thepresence of isofucosterol in Chattonella; and theoccurrence of brassicasterol, poriferasterol and fucosterol inOlisthodiscus luteus. High levels of eicosapentaenoic acid(EPA; 17-27% of fatty acids) were present in all raphidophyte species. Lipidcomposition correlated more closely to recent molecular classification ofraphidophytes than carotenoid pigments.

Differences in photoprotective pigment production between Japanese and Australian strains of Chattonella marina (Raphidophyceae)

Abstract Previous studies have shown that isolates of Chattonella marina from Australia and Japan exhibit differences in tolerance to high intensities of visible light. Here we show that the Australian strain of C. marina produces around five times more UV-absorbing mycosporine amino acids (MAAs) than the Japanese strain. This corresponds with 66% increased growth by the Australian strain under UVB exposure compared to no UV exposure. The MAA mycosporine–glycine, which reportedly acts as an antioxidant, was found in high quantity (110 fg cell –1 ) in the Australian but was absent in the Japanese strain. In contrast, changes in the concentration of violaxanthin and zeaxanthin per cell were 4.7–4.8 times greater in the Japanese relative to the Australian strain suggesting that the Japanese strain uses a xanthophyll cycle to moderate inhibition by high photosynthetically active radiation (PAR) irradiance. Increased MAA production under high irradiance was also observed in other Australian strains of Chattonella , but not noted in other Japanese strains suggesting ecophenotypic adaptation due to differing environmental conditions.