Heterocapsa cf. bohaiensis (dinoflagellate): identification and response to nickel and iron stress revealed through chlorophyll a fluorescence

Abstract

Metal toxicity in marine ecosystems is a growing issue owing to terrestrial runoff and anthropogenic pollution. Heterocapsa cf. bohaiensis, a newly isolated dinoflagellate from New Caledonia, was cultivated in photobioreactors operating continuously with high concentrations (10-3 M) of nickel (Ni2+) and/or iron (Fe2+) and their photosynthetic efficiency was assessed. The photosynthetic measurements indicated that H. cf. bohaiensis was tolerant to Ni2+ but sensitive to Fe2+ high concentrations. In the presence of Fe2+, maximum quantum efficiency and maximal relative electron transport rate decreased from 0.62 to 0.47 and from 156 to 102, respectively. The JIP-tests suggested a reduction of the photosynthesis in response to Fe2+ due to a disruption in the electron transport chain rather than a defect in the light absorption and trapping capacity which were on the contrary enhanced by Fe2+. These results bring new knowledge on the impact of nickel and iron on microalgae photosynthetic pathways.

Keywords

• dinoflagellate
• metal stress
• metallic trace elements
• microalgae
• pam fluorometry
• photosynthesis