Little is known about how active stream network expansion during rainstorms influences the ability of riparian buffers to improve water quality. We used aerial photographs to quantify stream network expansion during the wet winter season in five agricultural catchments in western Oregon, USA. Winter stream drainage densities were nearly two orders of magnitude greater than summer stream densities, and agricultural land use was much more abundant along transient portions (e.g. swales, road ditches) of stream networks. Water moving from agricultural fields into expanded stream networks during large hydrologic events has the opportunity to bypass downstream riparian buffers along perennial streams and contribute nonpoint-source pollutants directly into perennial stream channels.

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As part of the risk assessment of veterinary pharmaceuticals, the potential impact of these chemicals on soil ecosystems has to be determined according to European law. However, almost no data from standardized laboratory tests are available. Therefore, in the EU FP6 ERAPharm, the effects of the widely used veterinary pharmaceutical ivermectin, an anthelminthic, were studied in chronic laboratory tests performed according to OECD (Organisation for Economic Co-operation and Development) and ISO (International Organization for Standardization) guidelines. In detail, three soil invertebrate species--the earthworm Eisenia fetida, the springtail Folsomia candida, and the predatory mite Hypoaspis aculeifer--were tested. The nominal concentrations of ivermectin mixed into the test substrate artificial soil was verified using residue analysis, which indicated that the test substance is persistent for at least up to 28 days. As expected when considering the mode of action of this substance, survival and reproduction of collembolans were clearly affected [LC(50) = 8.4 mg/kg soil dry weight (dw); NOEC(repro) = 0.3 mg/kg soil (dw)]. Predatory mites reacted less sensitively [LC(50) > or = 31.6 mg/kg soil (dw); NOEC(repro) = 3.2 mg/kg soil (dw)]. Earthworm survival and reproduction were affected in the same order of magnitude as the predatory mites [LC(50) > or = 10 mg/kg soil (dw); NOEC(repro) = 2.5 mg/kg soil (dw)]. These results are in good agreement with the few data known from nonstandardized tests for the same or related soil invertebrate species. The results of these tests indicate that the effects of ivermectin on soil invertebrates--in particular, collembolans--cannot be excluded at field-relevant concentrations, as determined in a risk assessment according to VICH guidelines. More sophisticated higher-tier tests (e.g., in multispecies or semifield test systems) are recommended in order to assess the potential risk more accurately.

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Purpose Terrestrial ecotoxicology includes the investigation of the impact of chemicals on soils and soil-inhabiting organisms, whereby ecotoxicological effects are mainly assessed using single-species laboratory tests. As part of laboratory testing, reference substances, with known toxicity, are regularly used to confirm the sensitivity of the cultivated test organisms over time. Furthermore, reference substances are also applied in ring test evaluations for the validation of new test methods. The present work evaluates boric acid for its suitability as a potential reference substance for tests with higher plants and soil organisms (e.g., invertebrates and microbial communities). Materials and methods To enhance our existing knowledge, standardized acute and chronic laboratory tests with boric acid were performed and statistically evaluated using the following organism groups: microorganisms, higher plants, nematodes, enchytraeids, earthworms, collembolans, and beetles. Results and discussionThe results demonstrated that boric acid was amenable for use in standardized laboratory tests using a wide range of microbes, plants, and soil invertebrates. Methodological problems were not identified. In addition, several organism groups demonstrated a hormetic response that must be taken into consideration when determining appropriate test concentration ranges for the use of boric acid as a reference substance. Finally, it was clear that the sensitivity of the different test species differed by about an order of magnitude (with the exclusion of microorganisms), which seems little when considering the wide taxonomic and physiological range of the organisms tested. Conclusions Based on the present results boric acid can be considered as a suitable reference substance in soil ecotoxicology. It is also recommended that the suitability (i.e., sensitivity, robustness, and practicability) be proven in international ring tests.

The daily photosynthetic patterns of Cetraria cucullata were followed over the 1976 summer period at Anaktuvuk Pass, Alaska. With the exception of rainy peroids, the lichen exhibited a strong diurnal pattern with peak photosynthetic activity occurring between 0300 and 0700 h. This correllated with periods of maximal lichen water retention and the presence of direct solar radiation. When the lichen was moist, a strong gradient in photosynthetic activity was observed with no activity in the lichen bases and maximal activity in the lichen tips.

The effects of the fungicide carbendazim (formulation Derosal) on enchytraeids were determined in Terrestrial Model Ecosystem (TME) tests. TMEs consisted of intact soil columns (diameter 17.5 cm; length 40 cm) taken from three grassland sites (Amsterdam (The Netherlands), Bangor (Wales, England) and Flörsheim (Germany)) or an arable site (Coimbra (Portugal)). Results for each TME site were evaluated using the multivariate Principal Response Curve (PRC) method. The resulting No-Observable Effect Concentrations (NOECs) for the community were compared with the NOECs generated by univariate statistical methods. Furthermore, the EC(50)s (median effect concentrations) for the three taxa with the highest taxon weights determined by the PRC were compared with EC(50)s for the other endpoints. In eight out of 16 cases the PRC revealed the lowest NOEC for the enchytraeid species community. The lowest EC(50)s with the closest 95% confidence limits were calculated for the abundance of the three taxa with the highest taxon weights identified by the PRC. The EC(50)s ranging from 0.19-2.79 mg carbendazim/kg soil are similar to values from laboratory toxicity studies reported in the literature. Therefore, PRC is a useful instrument to analyse microcosm and mesocosm experiments; it allows for determination of NOECs for the species community (NOEC(community)), the evaluation of the taxa with the most pronounced treatment-related decrease in abundance and of the calculation of meaningful EC(50) values for those. The resulting NOEC(community) and EC(50) values offer a comprehensive tool for the risk assessment of chemicals at the ecosystem level.