Tânia Vidal

Acute and chronic toxicity of Betanal(®)Expert and its active ingredients on nontarget aquatic organisms from different trophic levels.

As a way to improve the efficacy to target organisms, new pesticide generation is based on technologically advanced coformulations of two or more active ingredients. One example is Betanal®Expert, a postemergence herbicide composed of an Advanced Micro Droplet coformulation of phenmedipham, desmedipham, and ethofumesate. Although its composed formulation brings an increase in the pesticide performance, it can also enhance its toxicity to nontarget species. Therefore, the present study intends to contribute with relevant information on ecotoxicological effects of Betanal®Expert and its active ingredients on a battery of bioassays using aquatic species from different trophic levels: bacteria (Vibrio fischeri), microalgae (Pseudokirchneriella subcapitata, Chlorella vulgaris, and Chlamydomonas pseudocostata), macrophyte (Lemna minor), and cladocerans (Daphnia magna and Daphnia longispina) species. Across the organisms tested and endpoints measured, different responses concerning the toxicity of the active ingredients were found: (i) phenmedipham was the most toxic to V. fischeri and L. minor; (ii) desmedipham was the most toxic to P. subcapitata, D. magna, and D. longispina; (iii) and ethofumesate was the most toxic to C. pseudocostata and C. vulgaris. Furthermore, for C. pseudocostata and daphnids, the toxicity observed for some active ingredients was higher than the toxicity of the commercial formulation. In fact, in an attempt to evaluate the contribution of each active ingredient to the overall toxicity of Betanal®Expert, it was observed that, in general, the toxicity values obtained for desmedipham and phenmedipham were close or even lower to the values determined for Betanal®Expert, indicating that the ethofumesate can act as an antagonist in the three‐way coformulation. In spite of the most impaired species being the photosynthetic ones, this study also showed pernicious effects on nonphotosynthetic organisms with distinct target sites. Therefore, our results underline the importance of clarifying the mode of action and metabolic pathways of these compounds on nonphotosynthetic species.

Phytoplankton dynamics in relation to seasonal variability and upwelling and relaxation patterns at the mouth of Ria de Aveiro (West Iberian Margin) over a four-year period

From June 2004 to December 2007, samples were weekly collected at a fixed station located at the mouth of Ria de Aveiro (West Iberian Margin). We examined the seasonal and inter-annual fluctuations in composition and community structure of the phytoplankton in relation to the main environmental drivers and assessed the influence of the oceanographic regime, namely changes in frequency and intensity of upwelling events, over the dynamics of the phytoplankton assemblage. The samples were consistently handled and a final subset of 136 OTUs (taxa with relative abundance > 0.01%) was subsequently submitted to various multivariate analyses. The phytoplankton assemblage showed significant changes at all temporal scales but with an overriding importance of seasonality over longer- (inter-annual) or shorter-term fluctuations (upwelling-related). Sea-surface temperature, salinity and maximum upwelling index were retrieved as the main driver of seasonal change. Seasonal signal was most evident in the fluctuations of chlorophyll a concentration and in the high turnover from the winter to spring phytoplankton assemblage. The seasonal cycle of production and succession was disturbed by upwelling events known to disrupt thermal stratification and induce changes in the phytoplankton assemblage. Our results indicate that both the frequency and intensity of physical forcing were important drivers of such variability, but the outcome in terms of species composition was highly dependent on the available local pool of species and the timing of those events in relation to the seasonal cycle. We conclude that duration, frequency and intensity of upwelling events, which vary seasonally and inter-annually, are paramount for maintaining long-term phytoplankton diversity likely by allowing unstable coexistence and incorporating species turnover at different scales. Our results contribute to the understanding of the complex mechanisms of coastal phytoplankton dynamics in relation to changing physical forcing which is fundamental to improve predictability of future prospects under climate change.

Resilience of the macroinvertebrate community of a small mountain river (Mau River, Portugal) subject to multiple stresses

Freshwaters commonly face human pressure, which produces multiple stressor scenarios that may threaten their ecological status. Biotic community assessments are useful tools to monitor such changes, and the European Water Framework Directive (WFD) has brought this into the legislative framework. The present study focused on a small mountain river facing multiple stresses, with the purpose of (1) evaluating the sensitivity of the macroinvertebrate community to the stresses, (2) assessing whether the ecological status was impaired in different years and (3) comparing the WFD approach with more refined community analyses. The river was generally in a very good ecological state. Despite seasonal and inter-annual fluctuations, no evident stressor-related effects were detected. We hypothesise that the observed resilience was the result of (1) the current dormant state of the abandoned mining areas (the most relevant potential source of contamination) and (2) the naturalness and strong current of the river, which buffered the impacts of contamination. Such a pattern may be generally valid for small mountain rivers, making them therefore more resilient to stresses. Nevertheless, small changes in community structure in the lowest reach of the river – undetected by the WFD assessment scheme – suggest that some disturbance was present, signalling the need for intervention by managers.

Ecotoxicological Assessment of Contaminated River Sites as a Proxy for the Water Framework Directive: an Acid Mine Drainage Case Study

Metal contamination of freshwater bodies resulting from mining activities or deactivated mines is a common problem worldwide such as in Portugal. Braçal (galena ore) and Palhal (pyrrhotite, chalcopyrite, galena, sphalerite, and pyrite ore), located in a riverside position, are both examples of deactivated mining areas lacking implemented recovery plans since their shutdown in the early mid-1900s. In both mining areas, effluents still flow into two rivers. The purpose of this work was to evaluate the potential hazard posed by the mining effluents to freshwater communities. Therefore, short- and long-term ecotoxicological tests were performed on elutriates from river sediments collected at each site using standard test organisms that cover different functional levels (Vibrio fischeri, Pseudokirchneriella subcapitata, Lemna minor, and Daphnia sp.). The results show that elutriates from the sediments of Palhal were very toxic to all tested species, while in contrast, elutriates from Braçal showed generally no toxicity for the tested species. Our study highlights the usefulness of using an ecotoxicological approach to help in the prioritization/scoring of the most critical areas impacted by deactivated mines. This ecotoxicological test battery can provide important information about the ecological status of each concerning site before investing in the application of time-consuming and costly methods defined by the Water Framework Directive or can stand as a meaningful complementary analysis.

Combined effect of copper sulfate and water temperature on key freshwater trophic levels – Approaching potential climatic change scenarios

This work relied on the use microcosms to evaluate the individual and the combined effects of different levels of copper sulfate (0.0, 0.013, 0.064 and 0.318mg Cu L-1) - a fungicide commonly exceeding allowable thresholds in agricultural areas - and a range of water temperature increase scenarios (15, 20 and 25°C) on freshwater species belonging to different functional groups. Hence, the growth inhibition of primary producers (the microalgae Raphidocelis subcapitata and the macrophyte Lemna minor), as well as the survival and feeding behavior of a shredder species (the Trichoptera Schizopelex sp.) were evaluated. The results revealed that copper was toxic to primary producers growth, as well as shredders growth and survival, being the growth of L. minor particularly affected. Higher water temperatures had generally enhanced the growth of primary producers under non-contaminated (microalgae and macrophytes) or low-contaminated (macrophytes) conditions. Despite the tendency for a more pronounced toxicity of copper under increasing water temperatures, a significant interaction between the two factors was only observed for microalgae. Since the test organisms represent relevant functional groups for sustaining freshwater systems functions, the present results may raise some concerns on the impacts caused by possible future climate change scenarios in aquatic habitats chronically exposed to the frequent or intensive use of the fungicide copper sulfate.

Is the aquatic toxicity of cationic polyelectrolytes predictable from selected physical properties

Cationic acrylamide-based polyelectrolytes (cPAM) are widely used in industry. They can be designed for optimal performance in a specific application, but this opportunity means the environmental safety of all different alternatives needs to be addressed. Both the inclusion of environmental toxicity as a design variable and the establishment of relationships between structure and ecotoxicity are thus current challenges. The aim of this study was to assess whether structural variables such as molecular weight, charge density and the integrative intrinsic viscosity parameter can be used to predict the environmental safety of cPAMs, as well as if these relationships are stable when the biological models change. Five cPAMs comprising molecular weight and charge density gradients were tested against bacteria, microalgae, macrophytes and daphnids. While correlations were found between physical properties of cPAMs as expected, no clear ecotoxicity patterns could be identified. All cPAMs can be classified as harmful to aquatic life on the basis of the responses elicited in the most sensitive organisms, microalgae and daphnids. Unicellular bacteria were the least sensitive eco-receptors possibly due to cell wall structure or the protective effect of the ionic strength of the test medium. The macrophytes were also tolerant to cPAMs exposure, which may be related to exposure avoidance mechanisms. The order of toxicity of cPAMs depended on the test organism, preventing the establishment of stable structure-ecotoxicity relationships. Therefore, the study leads to the overall generalist recommendation of relying on the most sensitively responding test organisms when developing new (eco)safe-by-design cPAMs.

Mixture toxicity assisting the design of eco-friendlier plant protection products: a case-study using a commercial herbicide combining nicosulfuron and terbuthylazine

The development of environmentally friendly plant protection products (PPPs), including pesticides, is a challenge nowadays. A commercial herbicide combining terbuthylazine and nicosulfuron as active substances (a.s.) was selected as a model PPP. The suitability of manipulating the ratio between a.s. towards alternative formulations with reduced impacts in a non-target indicator (Lemna minor) was assessed. The efficacy of such eco-friendlier a.s. ratios was then assessed using a target weed, Portulaca oleracea. Single and mixture toxicity testing with L. minor revealed an antagonistic joint action of the a.s., suggesting an environmentally protective effect of the combination compared to single dosing of a.s. The efficacy testing against the target weed of single and combined treatments of the a.s. showed that (i) the a.s. behave antagonistically throughout the whole P. oleracea response surface; (ii) there were no environmentally safe a.s. combinations ensuring target-efficacy; (iii) terbuthylazine alone was effective in controlling P. oleracea with no environmental hazardous potential, dosed at concentrations 10-fold lower than those involved in commercially recommended application doses. Overall, this case-study suggests that modelling tools widely used in the field of environmental risk assessment of PPPs may also have application in PPP design stages for a more efficient meeting of efficacy and environmental friendliness requirements.

Phytoplankton community-level bio-optical assessment in a naturally mercury contaminated Antarctic ecosystem (Deception Island)

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.

Ecotoxicological assessment of the herbicide Winner Top and its active substances—are the other formulants truly inert?

Formulants used in Plant Protection Products (PPPs) to promote their efficiency are normally undisclosed in the PPP documentation, unless they bear a human health or environmental hazardous potential per se. PPP regulation also demands the assessment of putative interactions among formulants within each product recipe and consequent effects, but these results are often unavailable. Such a case is that of the herbicide Winner Top (Selectis®, Portugal), which we selected as a model commercial formulation in the present study specifically aiming at (i) characterising its aquatic toxicity towards sensitive eco-receptors (Raphidocelis subcapitata, Chlorella vulgaris, Lemna minor and Lemna gibba), as well as that of its active substances (a.s.) nicosulfuron and terbuthylazine; (ii) comparing the ecotoxicity among the commercial formulation, the corresponding mixture of its a.s. and this a.s.’s mixture increasingly enriched with the formulants. Single chemical testing revealed that terbuthylazine was the strongest microalgae growth inhibitor and nicosulfuron was the strongest macrophyte growth inhibitor. On the other hand, the commercial formulation was consistently less toxic than the corresponding mixture of the a.s., suggesting that Winner Top formulants (72.9% of the commercial formulation) interact with the a.s., promoting less than additive effects in the selected non-target species. Importantly, this environmentally protective effect of the formulation can be apparent. Because macrophytes share most physiological features with the weeds targeted by the studied herbicide, it is likely that increased application doses are required to reach desired efficacy levels with the consequent detrimental increase of PPP residues load in edge-of-field freshwater ecosystems.