Methods for assessing the long-term toxicity of sediments to Hyalella azteca and Chironomus tentans can significantly enhance the capacity to assess sublethal effects of contaminated sediments through multiple endpoints. Sublethal tests allow us to begin to understand the relationship between short-term and long-term effects for toxic sediments. We present an interlaboratory evaluation with long-term and 10-d tests using control and contaminated sediments in which we assess whether proposed and existing performance criteria (test acceptability criteria [TAC]) could be achieved. Laboratories became familiar with newly developed, long-term protocols by testing two control sediments in phase 1. In phase 2, the 10-d and long-term tests were examined with several sediments. Laboratories met the TACs, but results varied depending on the test organism, test duration, and endpoints. For the long-term tests in phase 1, 66 to 100% of the laboratories consistently met the TACs for survival, growth, or reproduction using H. azrteca, and 70 to 100% of the laboratories met the TACs for survival and growth, emergence, reproduction, and hatchability using C. tentans. In phase 2, fewer laboratories participated in long-term tests: 71 to 88% of the laboratories met the TAC for H. azteca, whereas 50 to 67% met the TAC for C. tentans. In the 10-d tests with H. azteca and C. tentans, 82 and 88% of the laboratories met the TAC for survival, respectively, and 80% met the TAC for C. tentans growth. For the 10-d and long-term tests, laboratories predicted similar toxicity. Overall, the interlaboratory evaluation showed good precision of the methods, appropriate endpoints were incorporated into the test protocols, and tests effectively predicted the toxicity of sediments.
"The OC content was 0.98 ± 0.10% (n = 3) and CEC was 10.0 mEq/ 100 g. The high OC sediment used in the partitioning experiments was collected from West Bearskin Lake in Cook County, MN, USA (Leonard et al., 1999; Norberg-King et al., 2006). It was classified as sandy clay loam with 55%, 12%, and 33% sand, silt, and clay, respectively. "
[Show abstract][Hide abstract] ABSTRACT: Hydrophobic organic contaminants readily partition from aqueous to organic phases in aquatic systems with past research largely focusing on sediment. However, within many aquatic systems, matrices such as leaf material and detritus are abundant and ecologically important, as they may represent a primary exposure route for aquatic invertebrates. The objectives of the present study were to examine partitioning and toxicity to Hyalella azteca among permethrin and p,p'-DDT contaminated sediment, leaf, and a sediment-leaf mixture. Log organic carbon-water partitioning coefficients ranged from 4.21 to 5.82 for both insecticides, and were greatest within sediment and lowest in coarse leaf material. H. azteca lethal concentrations for 50% of the population (LC50s) ranged from 0.5 to 111μgg(-1) organic carbon, and were dependent on the matrix composition. The variation in sorption and toxicity among matrices common within stream ecosystems suggests that the ecological niche of aquatic organisms may be important for estimating risk of hydrophobic pesticides.
[Show abstract][Hide abstract] ABSTRACT: Chromium toxicity assessment of marine sediments in Peru is a topic of increasing interest. Mean lethal concentration of chromium (Cr+6) using the marine bivalve Donax obesulus Reeve 1854 (Pelecypoda: Donacidae) at 24 h, 48 h and 96 h of exposure was assessed, as well as its burying ability in a chromium (Cr+6) sediment. For D. obesulus acclimatization and rearing the marine microalga Dunaliella tertiolecta Butcher was employed. The assay was performed with 22.4 mm ± 1.5 mm D. obesulus adults. Mean lethal concentration (LC50) in chromium Cr +6 D. obesulus marine sediment was 410.4 mg·kg-1, 156.1 mg·kg-1 and 61.12 mg·kg-1 at 24 h, 48 h and 96 h of exposure, respectively. A guideline value proposed by Long et al. (1995) for chromium in an aquatic sediment is 370 mg·kg -1 . The results obtained in terms of LC50 at 48 h and 96 h for D. obesulus, exposed to chromium, were 57.8% and 83.5%, lower than the guideline value, respectively. Chromium presented a notorious sublethal effect on D. obesulus burying ability at 48 h of exposure. The protocol using D. obesulus has advantages in terms of sensibility, easy use, simplicity of reading, low cost and ecological realism.
[Show abstract][Hide abstract] ABSTRACT: In order to estimate acute-to-chronic toxicity ratios (ACRs) relevant to a coldwater stream community, we exposed rainbow trout (Oncorhynchus mykiss) to cadmium (Cd), lead (Pb), and zinc (Zn) in 96-h acute and 60+ day early-life stage (ELS) exposures. We also tested the acute and sublethal responses of a mayfly (Baetis tricaudatus) and a midge (Chironomus dilutus, formerly C. tentans) with Pb. We examine the statistical interpretation of test endpoints and the acute-to-chronic ratio concept. Increasing
the number of control replicates by 2 to 3× decreased the minimum detectable differences by almost half. Pb ACR estimates mostly increased with increasing acute resistance of the organisms (rainbow trout ACRs <≈ mayfly < Chironomus). The choice of test endpoint and statistical analysis influenced ACR estimates by up to a factor of four. When calculated using the geometric means of the no- and lowest-observed effect concentrations, ACRs with rainbow trout and Cd were 0.6 and 0.95; Zn about 1.0; and for Pb 3.3 and 11. The comparable Pb ACRs for the mayfly and Chironomus were 5.2 and 51 respectively. Our rainbow trout ACRs with Pb were about 5–20× lower than earlier reports with salmonids. We suggest discounting previous ACR results that used larger and older fish in their acute tests.
Water Air and Soil Pollution 11/2007; 188(1):41-66. DOI:10.1007/s11270-007-9524-8 · 1.55 Impact Factor
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