In situ evaluation of herbicide effects on the composition of river periphytic diatom communities in a region of intensive agriculture (original) (raw)
Related papers
Journal of Environmental Monitoring, 2011
Diatoms are commonly used as bioindicators of trophic and saprobic pollution in rivers. However, more knowledge is needed concerning their sensitivity to toxicants such as agricultural herbicides. In this study, seven species of periphytic diatoms were isolated from the Morcille River (Beaujolais area, France) which presents a streamward contamination gradient by pesticides and particularly diuron. The sensitivity of these species to diuron was assessed through ecotoxicological tests based on shortterm growth inhibition of monospecific cultures. After application of an appropriate toxicological model, EC50 were determined and the species were ranked according to their tolerance. EC50 values ranged from 4.5 to 19 mg L À1. Finally, the results were related to field periphyton samples from an upstream and a downstream site in order to check if variations in specific relative abundance between sites are consistent with differences in tolerance to diuron. Species distribution between sites was only partially in accordance with toxicological results suggesting that other factors (toxic or trophic) have an important influence on diatom communities in the river. Nevertheless, diatoms showed their potential to indicate water contamination by pesticides and toxic indices could be developed in complement to existing trophic indices.
Fresenius Environmental Bulletin
Periphytic diatoms are an important phototrophic component of river biofilm and are used in situ for the bioindication of pollution as well as in laboratory ecotoxicological tests to assess the toxicity of contaminants. In spring 2009, phototrophic biofilm samples mostly composed of diatoms were collected in a small river and their sensitivity to the herbicide diuron was estimated via photosynthesis bioassays. A large difference in tolerance to diuron was demonstrated between two periphytic communities from an upstream unpolluted site and a downstream site subjected to high seasonal contamination by pesticides. The comparison of diatom community structure between sites revealed important variations of the relative abundance of some species which could explain this difference. Consequently, some of these species were isolated from the river in autumn when toxic pressure was low, and kept in culture for more than six months in uncontaminated water. Acute toxicity tests of diuron based...
Annales de Limnologie - International Journal of Limnology, 2011
A microcosm experiment was carried out in order to test the effect of the herbicide metolachlor on river periphytic diatoms and to find potential diatom bioindicators of contamination. Effects were investigated at different biological organization levels (biofilm, diatom community, population and individual levels). The colonization of glass substrates by natural biofilm in artificial streams did not vary quantitatively between control and contaminated conditions (5 and 30 mg.L x1 ). However, non-parametric multivariate analysis of variance revealed a significant difference between contaminated and control diatom communities with regard to species composition. The difference was due to the greater development of probably tolerant species in the presence of the herbicide (e.g., Planothidium frequentissimum, Planothidium lanceolatum, Amphora montana, Surirella brebissonii and Nitzschia gracilis). An increase in the occurrence of abnormal forms was observed in relation to metolachlor concentration. In particular, up to 8% of the frustules of the species Surirella angusta exhibited prominent deformities. Monospecific acute toxicity tests were then performed on two species to estimate toxicity parameters based on growth inhibition. These tests also confirmed the teratogenic effect of the herbicide on S. angusta. This study shows that low concentrations of metolachlor in natural streams may significantly alter diatom community structure and that abnormal diatom forms should be taken into account in water contamination assessment.
The impacts of herbicides on the diatom communities found within the But Lake Channel
2011
A study was done of a channel off of Burt Lake to study the impacts of the herbicides being dumped into the area for human recreational purposes. Diatoms in particular were studied due to their ability to indicate environmental conditions of a system. Samples were done utilizing a plant squeezing technique and cellular counts. Shifts of multiple genera were discovered throughout the channel as the lake was approached. These shifts suggest a change in nutrient and pH levels from the first site to the last. I grant the Regents of the University of Michigan the non-exclusive right to retain, reproduce, and distribute my paper, titled in electronic formats and at no cost throughout the world. The University of Michigan may make and keep more than one copy of the Paper for purposes of security, backup, preservation and access, and may migrate the Paper to any medium or format for the purpose of preservation and access in the future.
Sensitivity of freshwater periphytic diatoms to agricultural herbicides
Aquatic Toxicology, 2009
The biomonitoring of pesticide pollution in streams and rivers using algae such as diatoms remains difficult. The responses of diatom communities to toxic stress in stream water are disturbed by the variations of environmental parameters. In this study, periphytic algae collected in situ were exposed under controlled conditions to two major herbicides used in French agriculture (isoproturon and s-metolachlor). Three exposure regimes were tested: 5 and 30 g L −1 for 6 days and 30 g L −1 for 3 days followed by a recovery period of 3 days. The algal biomasses were assessed from pigment concentrations (chlorophyll a and c) and from live cell density. The highest concentration (30 g L −1 ) of isoproturon inhibited the biomass increase statistically significantly. In periphyton exposed to 5 and 30 g L −1 of s-metolachlor, chlorophyll c concentration and live cell density were also statistically significantly lower than in the control. Periphyton left to recover after reduced exposure duration (3 days) showed higher growth rates after treatment with s-metolachlor than with isoproturon. Taxonomic identifications showed that species like Melosira varians, Nitzschia dissipata and Cocconeis placentula were not affected by the herbicide exposure. Other species like Eolimna minima and Navicula reichardtiana were more sensitive. Studying diatoms according to their trophic mode showed that facultative heterotroph species were statistically significantly favoured by isoproturon exposure at the highest concentration. Results obtained with s-metolachlor exposure showed a disturbance of cell multiplication rather than that of photosynthesis. These results suggest that photosynthesis inhibitors like isoproturon favour species able to survive when the autotroph mode is inhibited.
Although benthic diatoms are widely used in ecological studies of aquatic systems, there is still a dearth of data concerning species sensitivities towards several contaminants. Within the same community, different species may respond differently depending on their physiological and ecological characteristics. This lack of knowledge makes specific appropriate risk assessment impossible. To find out whether species sensitivity distribution (SSD) could be used to estimate the risk of herbicide toxicity for diatoms, we need to know whether their sensitivity depends on their physiological and ecological characteristics. We carried out single-species bioassays on 11 diatom species exposed to 8 herbicides. Dose-responses relationships were used to extrapolate the Effective Concentration 5 (EC 5 ) and the Effective Concentration 50 (EC 50 ) for each exposure. These data were used to fit a SSD curve for each herbicide, and to determine the Hazardous concentration 5 (HC 5 ) and 50 (HC 50 ). Our results revealed a high level of variability of the sensitivity in the set of species tested. For photosystem-II inhibitor (PSII) herbicides, diatoms species displayed a typical grouping of sensitivity levels consistent with their trophic mode and their ecological guild. N-heterotroph and ''motile'' guild species were more tolerant of PSII inhibitors, while Nautotroph and ''low profile'' guild species were more sensitive. Comprehensive SSD curves were obtained for 5 herbicides, but not for sulfonylurea herbicides or for dimetachlor, which had toxicity levels that were below the range of concentration tested. The SSD curves provided the following ranking of toxicity: diuron. terbutryn. isoproturon. atrazine. metolachlor. The HC that affected 5% of the species revealed that, even at the usual environmental concentrations of herbicides, diatom assemblages could be affected, especially by isoproturon, terbutryn, and diuron.
Science of The Total Environment, 2013
Benthic diatoms evolved in a biofilm structure, at the interface between water and substrata. Biofilms can adsorb toxicants, such as herbicides, but little is known about the exposure of biofilm organisms, such as benthic diatoms, to these adsorbed herbicides. We assessed the sensitivity of 11 benthic diatoms species to 6 herbicides under both planktonic and benthic conditions using single-species bioassays. The concentration that reduced the growth rate of the population by 10% (EC 10 ) and 50% (EC 50 ), respectively, varied depending on the species, the herbicides, and the growth forms involved. As a general trend, the more hydrophobic the herbicide, the more species were found to be sensitive under benthic growth conditions. Statistical differences (alpha b 5%) were observed between the sensitivities under planktonic and benthic growth conditions for many hydrophobic herbicides. A protective effect of the biofilm against herbicides was observed, and this tended to decrease (at both the EC 10 and EC 50 levels) with increasing hydrophobicity. The biofilm matrix appeared to control exposure to herbicides, and consequently their toxicity towards benthic diatoms. For metolachlor, terbutryn and irgarol, benthic thresholds derived from species sensitivity distributions were more protective than planktonic thresholds. For hydrophobic herbicides, deriving sensitivity thresholds from data obtained under benthic growth seems to offer a promising alternative.
PLoS ONE, 2012
Although benthic diatoms are widely used in ecological studies of aquatic systems, there is still a dearth of data concerning species sensitivities towards several contaminants. Within the same community, different species may respond differently depending on their physiological and ecological characteristics. This lack of knowledge makes specific appropriate risk assessment impossible. To find out whether species sensitivity distribution (SSD) could be used to estimate the risk of herbicide toxicity for diatoms, we need to know whether their sensitivity depends on their physiological and ecological characteristics. We carried out single-species bioassays on 11 diatom species exposed to 8 herbicides. Dose-responses relationships were used to extrapolate the Effective Concentration 5 (EC 5 ) and the Effective Concentration 50 (EC 50 ) for each exposure. These data were used to fit a SSD curve for each herbicide, and to determine the Hazardous concentration 5 (HC 5 ) and 50 (HC 50 ). Our results revealed a high level of variability of the sensitivity in the set of species tested. For photosystem-II inhibitor (PSII) herbicides, diatoms species displayed a typical grouping of sensitivity levels consistent with their trophic mode and their ecological guild. N-heterotroph and ''motile'' guild species were more tolerant of PSII inhibitors, while Nautotroph and ''low profile'' guild species were more sensitive. Comprehensive SSD curves were obtained for 5 herbicides, but not for sulfonylurea herbicides or for dimetachlor, which had toxicity levels that were below the range of concentration tested. The SSD curves provided the following ranking of toxicity: diuron. terbutryn. isoproturon. atrazine. metolachlor. The HC that affected 5% of the species revealed that, even at the usual environmental concentrations of herbicides, diatom assemblages could be affected, especially by isoproturon, terbutryn, and diuron.
Testing the response of benthic diatom assemblages to common riverine contaminants
Science of The Total Environment, 2021
• Diatom assemblage yield was proven a suitable ecotoxicological endpoint in rapid tests. • Two diatom assemblages (Good status) responded differently to contaminants. • Achnanthes, Fragilaria and Navicula were consistently the most responsive genera. • Diatom assemblage testing is a relevant asset supporting site-specific risk assessment.