Photochemical features and trace element substituted chlorophylls as early detection biomarkers of metal exposure in the model diatom Phaeodactylum tricornutum

• Autor(a) principal: Cabrita, Maria Teresa
• Data de Publicação: 2018
• Outros Autores: Duarte, Bernardo, Gameiro, Carla, Godinho, Rita M., Caçador, Isabel
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10451/39099
• topic: OJIP-test parameters; Trace element substituted chlorophylls; Biomarkers; Phaeodactylum tricornutum; Trace element stress early detection andassessment; Marine coastal areas

Establishing marine species equipped with efficient biomarkers of trace element stress is a major requirement forthe assessment of trace element contamination in marine ecosystems. This study investigates PS II overall ac-tivity and efficiency during light harvesting, electron transport chain (ETC) behaviour, OJIP-transient lightcurves, and pigment profiles, in the model marine diatom speciesPhaeodactylum tricornutumexposed to Cr, Co,Ni, Cu, Zn, Cd, Hg, Pb and to a mixture of all elements combined (Mix). OJIP-test parameters and trace elementsubstituted chlorophylls were investigated as potential biomarkers of stress induced by trace elements. Hg-exposed cells showed a shift in balance towards PS I activity, promoted by increase in the electron transport fromPQH2to the reduction of PS I end electron acceptors. Other elements had more limited effects, mostly affectingenergy dissipation and pigment levels to various degrees. Decoupling of PS II antennae connectivity was found inCo exposed cells. Chromium induced negative effects on PS I, but had no influence at the Oxygen EvolvingComplexes (OECs) level. Copper caused a shift in the equilibrium between PS towards the PS I by reducing the PSII efficiency. Cadmium induced damage in OECs of the PS II donor side, but had no effect on the energytransduction pathway, maintaining energy processing efficiency. Lead had no significant effect on the energytransduction pathway, but produced changes at pigment level, leading to an increase in the chlorophyll anddiadinoxanthin. In contrast, Ni had a beneficial role inP. tricornutumphotochemistry, leading to increasednumber of available RC and oxidized quinone pool size, possibly because concentrations used were not able toinduce severe cell damage. Copper, Cd and Zn led to substitution of Mg in chlorophyllamolecules, with theformation of less efficient CuChla, CdChlaand ZnChla. The biomarkers used evidenced the damaging effect ofCo, Cu, Cr, Pb, Hg and all trace elements combined (Mix), pointing to Hg as the most harmful element. Thesephysiological changes highlightP. tricornutumas a promising sentinel species for trace element contaminationand the proposed photochemical features suitable as an efficient battery of biomarkers for trace element stressearly detection in marine systems.