Can we predict community-wide effects of herbicides from toxicity tests on macrophyte species?

Macrophyte communities play an essential role in the way freshwater ecosystems function. It is thus of great concern to understand how environmental factors, especially anthropogenic ones, influence their composition and diversity. The aim of this study was to examine whether the effects of a herbicide mixture (50% atrazine, 35% isoproturon, 15% alachlor) on single macrophyte species can be used to predict its impact at a community level. In a first experiment we tested the sensitivity of six species (Azolla filiculoides, Ceratophyllum demersum, Elodea canadensis, Lemna minor, Myriophyllum spicatum and Vallisneria spiralis) grown separately and exposed to 0.6–600 gL−1 of the herbicide mixture. In a second experiment, conducted in microcosms, we tested the effects of herbicides on macrophyte assemblages composed of the same six species exposed to 0, 6 or 60 gL−1 of the herbicide mixture. Species grown separately exhibited growth inhibition at 60 and 600 gL−1. At 600 gL−1 the sensitivity differed significantly between species. V. spiralis was the most resistant species, C. demersum, M. spicatum and E. canadensis exhibited intermediate sensitivities, and A. filiculoides and L. minor were the most sensitive species. In microcosms, community biomass and Shannon evenness index were reduced after 8 weeks at 60 gL−1. Communities also exhibited changes in their composition: the relative and absolute abundance of C. demersum increased at 6 gL−1, while the relative abundance of V. spiralis increased at 60 gL−1. These results are in agreement with the individual responses of these species to the herbicides. It is therefore concluded that short-term effects of herbicides on simple macrophyte communities can be predicted from the sensitivity of individual species. However, further investigations are required to examine whether longer term effects can be predicted as well, especially in more complex communities

Toxicity in aquatic environments: discussion and evaluation methods

Aquatic toxicity tests are assays performed with different aquatic organisms of different ecological organization levels. Such tests are a source of information on the toxicity of a given substance or wastewater under controlled conditions, and they complement the physico-chemical analyses. Moreover, they allow one to evaluate the risks resulting from the presence of toxic substances in the environment. Algae, crustaceans, fishes and bacteria are frequently used in toxicity tests. In this work, we will present the main aspects related to the aquatic toxicity tests and a discussion of their applicability will also be presented.FAPES

Bioavailability of pesticides in freshwater sediments

In ecological risk assessment standardized sediment toxicity tests are used to predict the hazard of chemicals for sediment-living organisms. Feeding is a prerequisite in these long-term tests to avoid starvation of test organisms. Therefore, added food particles may act as vectors for the test compound. The importance of food particles as vectors, however, is dependent on several factors, for example, sorption and major uptake routes. In this thesis, laboratory experiments on the importance of pesticide sorption and uptake routes for the bioavailability to the midge Chironomus riparius in sediment toxicity test setups were performed. A feeding selectivity study showed that larvae almost exclusively fed on added food particles, and highly neglected sediment particles. Additionally, experiments on the sorption of the insecticide lindane, showed that food and peat particles (used in artificial sediment) efficiently sorbed lindane (>95% after 48 h). The binding strength of lindane was weak, facilitating particulate uptake. However, the uptake from dissolved lindane was higher than the uptake from particles. From this we concluded that toxicity may be underestimated in spiked-sediment scenarios, where hydrophobic pesticides sorb to the sediment and larvae to a large extent feed on uncontaminated food particles. Conversely, in a spiked-water scenario, the food particles may act as vector, resulting in a facilitated particulate uptake, in addition to the uptake from water. Sediment organic matter affects sorption, and thus bioavailability of pesticides. Pyrethroid toxicity was much higher in artificial sediment than in a natural sediment, indicating the simplicity and shortcomings of using artificial sediments. Interestingly, the sediment quality highly affected bioavailability in spiked-water. For example, C. riparus larvae in sediments with low organic matter content and exposed to spiked-water pyrethroids, showed lower survival, slower development, and increased adult size, than those in sediments with higher organic matter. The pyrethroid deltamethrin, showed an LC50-value (28 d) for C. riparius larvae in artificial sediment of 16 pg/L and 11 µg/kg for water- and sediment exposures, respectively, i.e. toxic effects occurred at concentrations lower than the detection limits for high-tech analytical methods. This thesis contributes to a wider understanding of processes affecting bioavailability in freshwater sediments, and in particular in standardized sediments used in toxicity testing. The understanding of test compound sorption and bioavailability is crucial for sound interpretations of toxicity tests and for the general credibility of such tests

Mersey & Weaver Fisheries Advisory Committee 22nd October, 1975.

This is the report from the Mersey and Weaver Fisheries Advisory Committee meeting, which was held on the 22nd October 1975. The report contains information on a report by the divisional scientist on fisheries activities, importation of live freshwater fish, drainage representation on local committees, new byelaws and fishing licence duties. The report by the divisional scientist looks at permissions for stocking and electrofishing, biological work and results of fish toxicity tests carried out in Rivers Bollin, Etherow, Glaze and Tame. It also contains records of fish mortalities. The Fisheries Advisory Committee was part of the Regional Water Authorities, in this case the North West Water Authority. This preceded the Environment Agency which came into existence in 1996

Short Communication: Effects of temperature and chemical formulation on the acute toxicity of pentachlorophenol to Simocephalus vetulus (Schoedler, 1858) (Crustacea: Cladocera)

The influence of temperature on the acute toxicity of a technical formulation (86%) and pure formulation (99%) of pentachlorophenol (PCP) to less than 24-h-old Simocephalus vetulus neonates was determined with 48-h static toxicity tests. The technical grade PCP was significantly more toxic to S. vetulus than the pure PCP (P < 0.05). Sensitivity of S. vetulus to technical PCP also significantly increased with temperature (P < 0.05), but a significant temperature effect was not found with the pure PCP. The mean 48-h LC50 values for neonates exposed to technical PCP were 140 and 199 ug l⁻¹ at 22deg.C and 16deg.C, respectively, and for those exposed to pure PCP were 262 and 304 ug l⁻¹, respectively