Development and validation of bio-optical ecotoxicological tests in marine phototrophs.

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Ecotoxicological effects of the anionic surfactant Sodium Dodecyl Sulfate (SDS) in two marine primary producers: Phaeodactylum tricornutum and Ulva lactuca

Publication . Cruz de Carvalho, Ricardo; Feijão, Eduardo; Matos, Ana; Cabrita, Maria Teresa; Utkin, Andrei; Novais, Sara; Lemos, Marco; Caçador, Isabel; Marques, João; Reis-Santos, Patrick; Fonseca, Vanessa; Duarte, Bernardo

Sodium Dodecyl Sulfate (SDS) is an anionic surfactant, extensively used in detergents, household and personal care products, as well as in industrial processes. The present study aimed to disclose the potential toxicological effects of SDS exposure under environmentally relevant concentrations (0, 0.1, 1, 3, and 10 mg L−1 ) on the physiology and biochemistry (photosynthesis, pigment, and lipid composition, antioxidative systems, and energy balance) of two marine autotrophs: the diatom Phaeodactylum tricornutum and the macroalgae Ulva lactuca. A growth rate (GR) reduction in P. tricornutum was observed with a classic dose-response effect towards the highest applied concentration, while a GR increase occurred in U. lactuca. Regarding photochemistry, the decrease in the fluorescence of the OJIP curves and laser-induced fluorescence allowed a better separation between SDS treatments in U. lactuca compared with P. tricornutum. Although all pigments significantly decreased in U. lactuca at the highest concentrations (except for antheraxanthin), no significant variations occurred in P. tricornutum. On the other hand, changes in fatty acid content were observed in P. tricornutum but not in U. lactuca. In terms of classical biomarker assessment, a dose-effect relationship of individual biomarkers versus SDS dose applied; U. lactuca displayed a higher number of biomarker candidates, including those in distinct metabolic pathways, increasing its usefulness for ecotoxicological applications. By evaluating the potential application of optical and biochemical traits, it was evident that the fatty acid profiles of the different exposure groups are excellent candidates in P. tricornutum, concomitant with the characteristics of this anionic surfactant. On the other hand, the results presented by laser-induced fluorescence and some parameters of PAM fluorometry in U. lactuca may be an advantage in the field, offering non-invasive, fast, easy-to-use, high-throughput screening techniques as excellent tools for ecotoxicology assessment.

2022Journal article

Open access

Unlocking Kautsky’s dark box: development of an optical toxicity classification tool (OPTOX index) with marine diatoms exposed to emerging contaminants

Publication . Duarte, Bernardo; Feijão, Eduardo; Cruz de Carvalho, Ricardo; Franzitta, Marco; Carlos Marques, João; Caçador, Isabel; Cabrita, Maria Teresa; Fonseca, Vanessa F.

Chlorophyll a induction curves, or Kautsky curves, have been extensively used to study physiological stress conditions in phototrophic organisms, with the analysis of several derived parameters. Nevertheless, these variables use only about 10 % of the information comprised in the complete Kautsky curve dataset, leaving 90 % of the photochemical data within an underutilized dark box, that is not translated into photochemically relevant variables. By observing the variable fluorescence profiles from marine diatoms exposed to a myriad of emerging and classical contaminants, several fluorescence profile alterations were detected, with significant deviations from the control conditions concomitant with the degree of growth inhibition imposed by the chemical stressor. The Linear Discriminant Analysis (LDA) analysis based on the normalized variable chlorophyll a fluorescence profiles revealed a high discriminatory efficiency of the type of contaminant to which the cultures were exposed, indicating that the exposure to different chemical stressors (contaminants) results in specific fluorescence profiles that can be used as descriptors of these exposure conditions. Analysing the individual contaminant LDA analysis, a very low overlap between samples exposed to different concentrations was observed, indicating a high discriminatory power of the variable fluorescence profiles. When evaluating the blind-test classification efficiencies, provided by this contaminant-specific LDA approach, it was possible to observe a high degree of efficiency in almost all contaminants tested, and for most of the concentrations applied. With this in mind, the produced linear discriminants and proportion of traces was used to compute an optical toxicity classification tool - the OPTOX index. The index revealed a high degree of correlation with the growth inhibition observed and/or with the exogenous dose of contaminant applied. The developed OPTOX index, a unifying tool enclosing all the fluorescence data provided by the chlorophyll a induction curve, proved to be an efficient tool to apply in ecotoxicological assays using marine model diatoms with a high degree of reliability for classifying the exposure of the cells to emerging contaminants. Additionally, the data analysis pipeline, as well as the index development methodology here proposed, can be easily transposed to other autotrophic organisms subjected to different ecotoxicological test conditions calibrated and validated against known biochemical or morphological descriptors of stress, integrating this way a large amount of data that was until know completely overlooked and left within an underutilized and undervalued dark box.

2021Journal article

Open access

Impacts of phytoplankton blooms on trace metal recycling and bioavailability during dredging events in the Sado estuary (Portugal)

Publication . Cabrita, Maria Teresa; Brito, Pedro; Caçador, Isabel; Duarte, Bernardo

This work evaluates the impact of phytoplankton blooms on metal availability driven by dredging, in an area of the Sado estuary (Portugal), subject to ongoing dredging operations during the entire sampling period. In situ changes of chlorophyll a concentration, bioavailable trace metals (Cr, Mn, Co, Ni, Cu, Zn, Cd and Pb) in the water column, metal content in particulate matter, and particulate metal to bioavailable metal ratios were investigated during pre-bloom, bloom and post-bloom conditions to evaluate the potential of the phytoplankton-mediated metal removal. Metals in particulate matter significantly enhanced concomitantly with the decline of metals (mostly Mn, Co, Cu, Zn, and Pb) in the water column during the bloom, in comparison with pre- and post-bloom periods. During the peak of the phytoplankton bloom, bioavailable Cr, Mn, Co, Ni, Cu, Zn, Cd and Pb were reduced to 30, 99, 100, 87, 98, 72, 84 and 88% of their original levels (pre-bloom values). Copper and Pb, and to a lesser extent, Zn and Mn, were ranked as more particle reactive. Volume particulate matter concentrations of Mn, Ni, Cu and Pb much higher than the bioavailable concentrations, indicated that phytoplankton is likely to be a dominant sink of these metals during the bloom period. Thus, Mn, Ni, Cu and Pb are prone to be transferred and biomagnified into the marine food web. These results highlight phytoplankton blooms as important biological sinks of trace metals during dredging, which should be taken into consideration in planning and management of dredging, to minimise environmental impacts and protect estuarine and coastal ecosystems.

2020Journal article

Restricted access

Effects of Glyphosate-Based Herbicide on Primary Production and Physiological Fitness of the Macroalgae Ulva lactuca

Publication . Carvalho, Ricardo Cruz; Feijão, Eduardo; Matos, Ana Rita; Cabrita, Maria Teresa; Utkin, Andrei B.

The use of glyphosate-based herbicides (GBHs) worldwide has increased exponentially over the last two decades increasing the environmental risk to marine and coastal habitats. The present study investigated the effects of GBHs at environmentally relevant concentrations (0, 10, 50, 100, 250, and 500 g L􀀀1) on the physiology and biochemistry (photosynthesis, pigment, and lipid composition, antioxidative systems and energy balance) of Ulva lactuca, a cosmopolitan marine macroalgae species. Although GBHs cause deleterious effects such as the inhibition of photosynthetic activity, particularly at 250 g L􀀀1, due to the impairment of the electron transport in the chloroplasts, these changes are almost completely reverted at the highest concentration (500 g L􀀀1). This could be related to the induction of tolerance mechanisms at a certain threshold or tipping point. While no changes occurred in the energy balance, an increase in the pigment antheraxanthin is observed jointly with an increase in ascorbate peroxidase activity. These mechanisms might have contributed to protecting thylakoids against excess radiation and the increase in reactive oxygen species, associated with stress conditions, as no increase in lipid peroxidation products was observed. Furthermore, changes in the fatty acids profile, usually attributed to the induction of plant stress response mechanisms, demonstrated the high resilience of this macroalgae. Notably, the application of bio-optical tools in ecotoxicology, such as pulse amplitude modulated (PAM) fluorometry and laser-induced fluorescence (LIF), allowed separation of the control samples and those treated by GBHs in different concentrations with a high degree of accuracy, with PAM more accurate in identifying the different treatments

2022Journal article

Open access