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- Zostera noltii development probing using chlorophyll a transient analysis (JIP-test) under field conditions: Integrating physiological insights into a photochemical stress indexPublication . Duarte, Bernardo; Pedro, Sílvia; Marques, J. C.; Adão, Helena; Caçador, IsabelBeyond their undeniable role, nowadays we also must look to seagrass beds as endangered environmentswith urgent monitoring and conservation needs. In the present study Z. noltii photochemical performanceof under different stages of development/recovery was assessed and its results applied in the develop-ment of a photochemical stress index (PSI) to classify and efficiently assess the physiological conditionof seagrass beds. In order to investigate deeper into this metabolic network the JIP-test was applied,allowing to identify the reasons underlying the first signs of stress. Less developed beds low connectiv-ity between PS II antennae leading inevitably to an impairment of the energetic transport. Associatedto this also the quinone pool showed severe depletion both in number and function. Alongside the K-step presence in the Kautsky curve points to severe damage at donor side of the PS II, where the OxygenEvolving Complexes (OECs) are located. All these negative impacts increase the quantum yield of the non-photochemical reactions in stressed/less developed seagrass beds. In sum, more developed beds showproportionally higher light use efficiencies promoted by a higher number of oxidized reaction centrescoupled with an enhanced capacity in using the generated electron potential and relatively lower energydissipations. Coupling all the photochemical into an Integrated Biomarker Response (IBR) approach, aphotochemical stress index (PSI) was produced. The PSI showed that more developed sites present lowerphotochemical stress values with inverse significant correlation with biomass coverage, reinforcing theapplicability of this non-invasive index as a reflex of the seagrass bed development stage.
- Ecotoxicity of the lipid-lowering drug bezafibrate on the bioenergetics and lipid metabolism of the diatom Phaeodactylum tricornutumPublication . Duarte, Bernardo; Prata, Diogo; Matos, Ana Rita; Cabrita, Maria Teresa; Caçador, Isabel; Marques, J. C.; Cabral, Henrique; Reis Santos, Patrick; Fonseca, VanessaPharmaceutical residues impose a new and emerging threat to the marine environment and its biota. In most countries, ecotoxicity tests are not required for all pharmaceutical residues classes and, even when mandatory, these tests are not performed using marine primary producers such as diatoms. These microalgae are among the most abundant class of primary producers in the marine realm and key players in the marine trophic web. Blood-lipid-lowering agents such as bezafibrate and its derivatives are among the most prescribed drugs and most frequently found human pharmaceuticals in aquatic environments. The present study aims to investigate the bezafibrate ecotoxicity and its effects on primary productivity and lipid metabolism, at environmentally relevant concentrations, using the model diatom Phaeodactylum tricornutum. Under controlled conditions, diatom cultures were exposed to bezafibrate at 0, 3, 6, 30 and 60 μg L-1, representing concentrations that can be found in the vicinity of discharges of wastewater treatment plants. High bezafibrate concentrations increased cell density and are suggested to promote a shift from autotrophic to mixotrophic metabolism, with diatoms using light energy generated redox potential to breakdown bezafibrate as carbon source. This was supported by an evident increase in cell density coupled with an impairment of the thylakoid electron transport and consequent photosynthetic activity reduction. In agreement, the concentrations of plastidial marker fatty acids showed negative correlations and Canonical Analysis of Principal coordinates of the relative abundances of fatty acid and photochemical data allowed the separation of controls and cells exposed to bezafibrate with high classification efficiency, namely for photochemical traits, suggesting their validity as suitable biomarkers of bezafibrate exposure. Further evaluations of the occurrence of a metabolic shift in diatoms due to exposure to bezafibrate is paramount, as ultimately it may reduce O2 generation and CO2 fixation in aquatic ecosystems with ensuing consequences for neighboring heterotrophic organisms.
- Phytoplankton community-level bio-optical assessment in a naturally mercury contaminated Antarctic ecosystem (Deception Island)Publication . Duarte, Bernardo; Cabrita, Maria Teresa; Vidal, Tânia; Pereira, Joana Luísa; Pacheco, Mário; Pereira, Patrícia; Canário, João; Gonçalves, Fernando J.M.; Matos, Ana Rita; Rosa, Rui; Marques, J. C.; Caçador, Isabel; Gameiro, C.Mercury naturally contaminated environments, like Deception Island (Antarctica), are field labs to study the physiological consequences of chronic Hg-exposure at the community level. Deception Island volcanic vents lead to a continuous chronic exposure of the phytoplanktonic communities to potentially toxic Hg concentrations. Comparing Hg-contaminated areas (Fumarolas Bay - FB, Gabriel de Castilla station - GdC station), no significant differences in chlorophyll a concentrations were detected, indicating that biomass production was not impaired by Hg-exposure despite the high Hg levels found in the cells. Moreover, the electron transport energy, responsible for energy production, also presented rather similar values in phytoplankton from both locations. Regarding FB communities, although the cells absorbed and trapped lower amounts of energy, the effect of Hg was not relevant in the photochemical work produced by the electronic transport chain. This might be due to the activation of alternative internal electron donors, as counteractive measure to the energy accumulated inside the cells. In fact, this alternative electron pathway, may have allowed FB communities to have similar electron transport energy fluxes without using respiration as photoprotective measure towards excessive energy. Hg-exposed cells also showed a shift from the energy flux towards the PS I (photosystem I), alleviating the excessive energy accumulation at the PS II (photosystem II) and preventing an oxidative burst. Our findings suggest a higher energy use efficiency in the communities exposed to volcanic Hg, which is not observable in cultured phytoplankton species grown under Hg exposure. This may constitute a metabolic adaptation, driven from chronic exposure allowing the maintenance of high levels of primary productivity under the assumingly unfavourable conditions of Deception Island.