Abstract-A sediment contact test (SCT) battery consisting of five ecotoxicological test systems was applied to 21 native freshwater sediments characterized by a broad variety of geochemical properties and anthropogenic contamination. Higher plants (Myriophyllum aquaticum), nematodes (Caenorhabditis elegans), oligochaetes (Lumbriculus variegatus), zebrafish embryos (Danio rerio), and bacteria (Arthrobacter globiformis), representing various trophic levels and exposure pathways, were used as test organisms. The test battery detected sediment toxicity caused by anthropogenic pollution, whereas the various tests provided site-specific, nonredundant information to the overall toxicity assessment. Based on the toxicity pattern derived from the test battery, the sediments were classified according to a newly proposed classification system for sediment toxicity assessment. The SCT-derived classification generally agreed well with the application of consensus-based sediment quality guidelines (SQGs), especially with regard to sediments with high toxic potential. For sediments with low to medium toxic potential, the SQGs often underestimated the toxicity that was detected by the SCTs, underpinning the need for toxicity tests in sediment quality assessment. Environ. Toxicol. Chem. 2013;32:144-155. # 2012 SETAC
A whole-sediment toxicity test with Myriophyllum aquaticum has been developed by the German Federal Institute of Hydrology and standardized within the International Organization for Standardization (ISO; ISO 16191). An international ring-test was performed to evaluate the precision of the test method. Four sediments (artificial, natural) were tested. Test duration was 10 d, and test endpoint was inhibition of growth rate (r) based on fresh weight data. Eighteen of 21 laboratories met the validity criterion of r ≥ 0.09 d(-1) in the control. Results from 4 tests that did not conform to test-performance criteria were excluded from statistical evaluation. The inter-laboratory variability of growth rates (20.6%-25.0%) and inhibition (26.6%-39.9%) was comparable with the variability of other standardized bioassays. The mean test-internal variability of the controls was low (7% [control], 9.7% [solvent control]), yielding a high discriminatory power of the given test design (median minimum detectable differences [MDD] 13% to 15%). To ensure these MDDs, an additional validity criterion of CV ≤ 15% of the growth rate in the controls was recommended. As a positive control, 90 mg 3,5-dichlorophenol/kg sediment dry mass was tested. The range of the expected growth inhibition was proposed to be 35 ± 15%. The ring test results demonstrated the reliability of the ISO 16191 toxicity test and its suitability as a tool to assess the toxicity of sediment and dredged material.
Purpose Previous studies have shown that ivermectin, a widely used parasiticide, is very toxic to many non-target invertebrate species. In view of the strong binding of ivermectin to sediments and the scarcity of data on chronic toxicity to freshwater sediment invertebrates, chronic effects of the parasiticide on the midge Chironomus riparius and the oligochaete Lumbriculus variegatus were investigated. Materials and methods C. riparius and L. variegatus were exposed for up to 28 days to ivermectin-spiked artificial sediment. Nominal ivermectin concentrations were 3.1 to 50µg/kg dry sediment in the Chironomus test and 50 to 5,000µg/kg dry sediment in the Lumbriculus test. The evaluated endpoints were survival, growth, emergence ratio and development rate for C. riparius, and survival/ reproduction and total biomass for L. variegatus. Results and discussion Ivermectin had a significant, concentration-dependent effect on larval survival and growth, emergence and development rate of C. riparius. With a lowest observed effect concentration (LOEC) of 6.3µg/kg dry sediment, larval dry weight was the most sensitive endpoint. L. variegatus was considerably less sensitive to ivermectin than C. riparius. A LOEC of 500µg/kg dry sediment was derived for effects on survival/reproduction and total biomass. Conclusions The results of the present study, especially the high toxicity of ivermectin to C. riparius, indicate that the potential impact of ivermectin on freshwater benthic invertebrates deserves further attention.
Bioaccumulation factors (BAFs) are often used in the risk assessment process to estimate trophic transfer of contaminants such as metals from soil. BAFs can be derived from laboratory studies through the determination of steady-state concentrations or kinetic estimation methods. In this study, bioaccumulation tests were performed with artificial soil spiked at low levels with cadmium or zinc to determine uptake and elimination kinetics of both metals by the compost worm Eisenia andrei. The metal-amended soils were acclimated for 21 days prior to the test, after which worms were individually incubated in the soils. The uptake phase comprised 0-21 days, after which the test organisms were transferred into clean soil and the elimination phase continued for an additional 21 days. Subsamples of soil and earthworms (whole body) were collected from independent replicates throughout the uptake phase and elimination phase and analyzed for total metal concentrations. Uptake of Cd in E. andrei increased linearly with time and did not reach steady state within the testing period. Cd uptake and excretion were described by a one-compartment first-order kinetics model. Zn concentrations rapidly increased in E. andrei after 1 day of exposure but subsequently decreased to background levels throughout the remainder of the uptake phase; internal Zn concentrations did not change from background levels during the elimination phase. Kinetic BAFs were calculated for Cd and Zn. Cd is a nonessential metal that is bioaccumulated at a relatively rapid rate, while Zn is an essential metal, and as such, it is regulated by E. andrei. Metal essentiality and concentration significantly impact bioaccumulation of metals by terrestrial invertebrates.
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