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- Halophyte fatty acids as biomarkers of anthropogenic-driven contamination in Mediterranean marshes: Sentinel species survey and development of an integrated biomarker response (IBR) indexPublication . Duarte, Bernardo; Carreiras, João; Pérez-Romero, Jesús Alberto; Mateos-Naranjo, Enrique; Redondo-Gómez, Susana; Matos, Ana Rita; Marques, J. C.; Caçador, IsabelEstuarine environments are extremely affected by anthropogenic-driven contamination, namely heavy metals. In the recent years, several organisms have been studied to be used as sentinel species providing a wide range of biomarkers for estuarine contamination. Only recently non-traditional biomarkers, such as fatty acids, were included in animal ecotoxicology and impact assessment studies. Nevertheless, there is a wide lack of knowledge regarding to its application in estuarine plants. Considering this the present work aimed to evaluate the application of fatty acid profiling in Mediterranean halophytic species chronically exposed to different degrees of metal contamination, while incorporating these fatty acid biomarkers into an unifying index. From the fatty acids analysis two different types of sentinel halophytes could be identified: the contamination sensitive Halimione portulacoides (sea purslane), Sarcocornia fruticosa (glasswort) and Spartina patens (saltmeadow cordgrass), and the contamination-tolerant Spartina maritima (small cordgrass). In sensitive species the most evident changes in the fatty acid profiles were the decrease in the 18:3 and the increase in the 16:0 fatty acid relative concentrations, while the inverse trend was recorded in the tolerant S. maritima under chronic contamination. Beyond the evident physiological importance, these shifts in the halophyte fatty acid profiles provide some understanding on their use as biomarkers of metal contamination. After application of an integrated biomarker response (IBR) index it was possible to conclude that in sensitive halophytes (H. portulacoides, S. fruticosa and S. patens) the samples collected from the contaminated site produce had higher IBR values than the tolerant species S. maritima being these lower values linked with an adaptation mechanism towards contamination. Furthermore, the fatty acid-based IBR index was intrinsically connected with the bioavailable metals concentrations in the rhizosediments, which make that it could be used in future impact assessment and/or ecotoxicology studies. In summary, the data showed that two of the most abundant halophytes in the Mediterranean eco-region (S. fruticose and H. portulacoides) are potential sentinel species of metal contamination, whereas its fatty acid profile is an efficient biomarker of the degree of environmental contamination.
- Heat wave impacts on the model diatom Phaeodactylum tricornutum: Searching for photochemical and fatty acid biomarkers of thermal stressPublication . Feijão, Eduardo; Gameiro, C.; Franzitta, Marco; Duarte, Bernardo; Caçador, Isabel; Cabrita, Maria Teresa; Matos, Ana RitaGlobal warming is increasing the frequency and intensity of extreme thermal events, with inevitable consequences for marine ecosystems and organisms. Phytoplankton is at the base of marine food webs and diatoms are major contributors to global primary production. Therefore, environmental changes, such as heat, influencing growth, physiology and biochemical composition of diatoms, impact other organisms at higher trophic levels. The model diatom Phaeodactylum tricornutum, particularly rich in the long chain omega-3 eicosapentaenoic acid (EPA), and able to accumulate substantial amounts of storage lipids, has recently been the object of numerous works, regarding fundamental aspects of lipid metabolism and exploring its biotechnological potential for biodiesel and aquaculture purposes. The aim of this study was to use P. tricornutum, growing under controlled conditions, to examine the effects of a heat wave, in order to identify heat stress biomarkers. The photosynthetic and respiratory metabolism was investigated by Chlorophyll a fluorescence and by O2 evolution and discussed in connection with changes observed in the composition of photosynthetic pigments and fatty acids. Phaeodactylum tricornutum cells exposed to 26 °C displayed lower photosynthetic O2 production, but similar respiratory rate, comparing to cells at control temperature (18 °C), which is likely related to the biomass decrease observed under heat stress. Heat wave exposed cells also showed a less efficient PSII, higher energy dissipation and higher chlorophyll a and fucoxanthin concentrations, suggesting a heat-induced amplification of the light energy absorption capacity. Heat wave exposed cells showed lower relative EPA contents and double bond indexes, whereas the parameter inversely related to nutritional value, omega 6/omega 3 ratio, increased. Moreover, the analysis of the fatty acid profiles also suggested that heat exposure negatively impacted thylakoid lipids, in agreement with the decrease observed in photosynthesis. Results obtained highlight the negative impact of heat waves on diatom photosynthesis and nutritional value, as well as on their capacity to oxygenate ocean water. Furthermore, physiological parameters as well as fatty acids and photosynthetic pigments signatures, were identified, that could represent expedite biomarkers of thermal stress in future studies.
- Photochemical features and trace element substituted chlorophylls as early detection biomarkers of metal exposure in the model diatom Phaeodactylum tricornutumPublication . Cabrita, Maria Teresa; Duarte, Bernardo; Gameiro, C.; Godinho, Rita M.; Caçador, IsabelEstablishing marine species equipped with efficient biomarkers of trace element stress is a major requirement for the assessment of trace element contamination in marine ecosystems. This study investigates PS II overall activity and efficiency during light harvesting, electron transport chain (ETC) behaviour, OJIP-transient light curves, and pigment profiles, in the model marine diatom species Phaeodactylum tricornutum exposed to Cr, Co, Ni, Cu, Zn, Cd, Hg, Pb and to a mixture of all elements combined (Mix). OJIP-test parameters and trace element substituted 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 from PQH2 to the reduction of PS I end electron acceptors. Other elements had more limited effects, mostly affecting energy dissipation and pigment levels to various degrees. Decoupling of PS II antennae connectivity was found in Co exposed cells. Chromium induced negative effects on PS I, but had no influence at the Oxygen Evolving Complexes (OECs) level. Copper caused a shift in the equilibrium between PS towards the PS I by reducing the PS II efficiency. Cadmium induced damage in OECs of the PS II donor side, but had no effect on the energy transduction pathway, maintaining energy processing efficiency. Lead had no significant effect on the energy transduction pathway, but produced changes at pigment level, leading to an increase in the chlorophyll and diadinoxanthin. In contrast, Ni had a beneficial role in P. tricornutum photochemistry, leading to increased number of available RC and oxidized quinone pool size, possibly because concentrations used were not able to induce severe cell damage. Copper, Cd and Zn led to substitution of Mg in chlorophyll a molecules, with the formation of less efficient CuChl a, CdChl a and ZnChl a. The biomarkers used evidenced the damaging effect of Co, Cu, Cr, Pb, Hg and all trace elements combined (Mix), pointing to Hg as the most harmful element. These physiological changes highlight P. tricornutum as a promising sentinel species for trace element contamination and the proposed photochemical features suitable as an efficient battery of biomarkers for trace element stress early detection in marine systems.