Quantification of toxic effects of the herbicide metolachlor on marine microalgae Ditylum brightwellii (Bacillariophyceae), Prorocentrum minimum (Dinophyceae), and Tetraselmis suecica (Chlorophyceae) (original) (raw)
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Hazard and risk of herbicides for marine microalgae
Environmental Pollution, 2014
Due to their specific effect on photosynthesis, herbicides pose a potential threat to coastal and estuarine microalgae. However, comprehensive understanding of the hazard and risk of these contaminants is currently lacking. Therefore the aim of the present study was to investigate the toxic effects of four ubiquitous herbicides (atrazine, diuron, Irgarol Ò 1051 and isoproturon) and herbicide mixtures on marine microalgae. Using a Pulse Amplitude Modulation (PAM) fluorometry based bioassay we demonstrated a clear species and herbicide specific toxicity and showed that the current environmental legislation does not protect algae sufficiently against diuron and isoproturon. Although a low actual risk of herbicides in the field was demonstrated, monitoring data revealed that concentrations occasionally reach potential effect levels. Hence it cannot be excluded that herbicides contribute to observed changes in phytoplankton species composition in coastal waters, but this is likely to occur only occasionally.
Additive toxicity of herbicide mixtures and comparative sensitivity of tropical benthic microalgae
Marine Pollution Bulletin, 2010
Natural waters often contain complex mixtures of unknown contaminants potentially posing a threat to marine communities through chemical interactions. Here, acute effects of the photosystem II-inhibiting herbicides diuron, tebuthiuron, atrazine, simazine, and hexazinone, herbicide breakdown products (desethyl-atrazine (DEA) and 3,4-dichloroaniline (3,4-DCA)) and binary mixtures, were investigated using three tropical benthic microalgae; Navicula sp. and Cylindrotheca closterium (Ochrophyta) and Nephroselmis pyriformis (Chlorophyta), and one standard test species, Phaeodactylum tricornutum (Ochrophyta), in a high-throughput Maxi-Imaging-PAM bioassay (Maxi-IPAM). The order of toxicity was; diuron > hexazinone > tebuthiuron > atrazine > simazine > DEA > 3,4-DCA for all species. The tropical green alga N. pyriformis was up to 10-fold more sensitive than the diatoms tested here and reported for coral symbionts, and is recommended as a standard tropical test species for future research. All binary mixtures exhibited additive toxicity, and the use of herbicide equivalents (HEq) is therefore recommended in order to incorporate total-maximum-load measures for environmental regulatory purposes.
The Korean Journal of Microbiology, 2016
Microalgae are the potential bioindicators of environmental changes, for the environmental risk assessment as well as to set limits for toxic chemical release in the aquatic environment. Here, we evaluated the effects of two endocrine disrupting chemicals (EDCs), namely bisphenol A (BPA) and Aroclor 1016, on the green algae Tetraselmis suecica, diatom Ditylum brightwellii, and dinoflagellate Prorocentrum minimum. Each species showed wide different sensitivity ranges when exposed to these two EDCs; the 72 h effective concentration (EC50) for these test species showed that Aroclor 1016 was more toxic than BPA. EC50 values for the diatom D. birghtwellii were calculated at 0.037 mg/L for BPA and 0.002 mg/L for Aroclor 1016, representing it was the most sensitive when compared to the other species. In addition, these results suggest that these EDC discharge beyond these concentrations into the aquatic environments may cause harmful effect to these marine species.
Toxicity of ten herbicides to the tropical marine microalgae Rhodomonas salina
Scientific Reports
Herbicide contamination of nearshore tropical marine ecosystems is widespread and persistent; however, risks posed by most ‘alternative’ herbicides to tropical marine microalgae remain poorly understood. Experimental exposures of the important but understudied microalgae Rhodomonas salina to seven individual Photosystem II (PSII) inhibitor herbicides (diuron, metribuzin, hexazinone, tebuthiuron, bromacil, simazine, propazine) led to inhibition of effective quantum yield (ΔF/Fm′) and subsequent reductions in specific growth rates (SGR). The concentrations which reduced ΔF/Fm′ by 50% (EC50) ranged from 1.71-59.2 µg L−1, while the EC50s for SGR were 4-times higher, ranging from 6.27-188 µg L−1. Inhibition of ΔF/Fm′ indicated reduced photosynthetic capacity, and this correlated linearly with reduced SGR (R2 = 0.89), supporting the application of ∆F/Fm’ inhibition as a robust and sensitive indicator of sub-lethal toxicity of PSII inhibitors for this microalga. The three non-PSII inhibito...
1998
Twelve indoor, plankton-dominated, freshwater microcosms (600 l) were used to study the effect of a mixture of herbicides on structural and functional aspects of these ecosystems. The EC 50, 72 h values of the most susceptible standard test alga Selenastrum capricornutum (EC 50, atrazine = 54 µg l −1 , EC 50, diuron = 15 µg l −1 , EC 50, metolachlor = 56 µg l −1 ) were used as a starting point for the dosage applied in the microcosms (dosages: 0, 0.01, 0.03, 0.1, 0.3, 1× EC 50 ). The microcosms were exposed to chronic levels for 28 days and subsequently monitored for 4 more weeks.
Comparative effects of herbicides on photosynthesis and growth of tropical estuarine microalgae
Marine Pollution Bulletin, 2008
Pulse amplitude modulation (PAM) fluorometry is ideally suited to measure the sub-lethal impacts of photosystem II (PSII)-inhibiting herbicides on microalgae, but key relationships between effective quantum yield [Y(II)] and the traditional endpoints growth rate (l) and biomass increase are unknown. The effects of three PSII-inhibiting herbicides; diuron, hexazinone and atrazine, were examined on two tropical benthic microalgae; Navicula sp. (Heterokontophyta) and Nephroselmis pyriformis (Chlorophyta). The relationships between Y(II), l and biomass increase were consistent (r 2 P 0.90) and linear (1:1), validating the utility of PAM fluorometry as a rapid and reliable technique to measure sub-lethal toxicity thresholds of PSII-inhibiting herbicides in these microalgae. The order of toxicity (EC 50 range) was: diuron (16-33 nM) > hexazinone (25-110 nM) > atrazine (130-620 nm) for both algal species. Growth rate and photosynthesis were affected at diuron concentrations that have been detected in coastal areas of the Great Barrier Reef.
Effects of herbicide mixtures on freshwater microalgae with the potential effect of a safener
Annales de Limnologie - International Journal of Limnology, 2019
Freshwater microalgae are primary producers and cosmopolitan species subjected to the effects of herbicides. In this work, the in vitro algal growth inhibitory effects of 11 agrochemicals (9 herbicides, 1 metabolite, and 1 safener) were quantified. Chemical compounds were applied singly and in specific mixtures. Three species were used in axenic condition: the green alga Desmodesmus subspicatus (Chodat), the diatoms Nitzschia palea (Kützing) W. Smith and Navicula pelliculosa (Kützing) Hilse. When exposed to single compounds, N. palea and N. pelliculosa were only sensitive to atrazine/desethylatrazine and the safener benoxacor (BE), respectively. D. subspicatus was equally sensitive to four herbicides including atrazine and its metabolite and significantly more sensitive to iodosulfuron-methyl-sodium (IODO). The mixture of these five compounds induced a significantly higher growth inhibition of about 1.5-fold than IODO alone, which could be attributed to the four other herbicides. Th...
Microalgal reactions to water polluting herbicide Plugaru et al Studia UBB Chemia 2017
The aim of the study is to compare biochemical and physiological reactions of two related species of green microalgae (Scenedesmus acuminatus and Scenedesmus opoliensis), both considered suitable for bioindication and remediation of aquatic environments polluted with herbicides. Monoalgal axenic cultures were treated for 10 days under controlled conditions with different concentrations (from 0.1 μM to 100 µM) of glufosinate (a nonselective contact herbicide that inhibits glutamine synthase activity, thus disturbing photorespiration, inhibiting photosynthetic carbon assimilation, and generating ammonium excess in plant cells). S. opoliensis was found to be a better indicator of adverse effects of glufosinate than S. acuminatus. Changes in the ground chlorophyll fluorescence (reflecting light energy harvesting capacity), in cell division rate and in chlorophyll-a content may be early, costeffective and sensitive markers of herbicide impact on microalgal communities inhabiting polluted water. Our results bring new data concerning the need of selection among related test organisms based on differentiated tolerance, as well as concerning biochemical parameters suitable for evaluation of water pollution impact when organic xenobiotics accumulate in aquatic environments. Thus, the presented results may be applied in optimizing bioindication of water quality using microalgae, and in treatment of wastewater polluted due to agricultural practices.
Toxic pressure of herbicides on microalgae in Dutch estuarine and coastal waters
Journal of Sea Research, 2015
Estuarine and coastal waters which chemical analysis of water was performed and also a toxicity assessment using the Pulse Amplitude Modulation (PAM) fluorometry assay that measures ΦPSII. The toxic pressure on ΦPSII in microalgae has decreased with 55-82% from 2003 to 2012, with the Western Scheldt estuary showing the highest toxic pressure. By combining toxicity data from the PAM assay with chemical analysis of herbicide concentrations, we have identified diuron and terbutylazine as the main contributors to the toxic pressure on microalgae. Although direct effects are not expected, the toxic pressure is close to the 10% effect level in the PAM assay. A compliance check with the current environmental legislation of the European Union revealed that the quality standards are not sufficient to protect marine microalgae.