Interlaboratory Study of Precision: Hyalella Azteca and Chironomus Tentans Freshwater Sediment Toxicity Assays

Abstract

Abstract-Standard 10-d whole-sediment toxicity test methods have recently been developed by the U.S. Environmental Protection Agency (EPA) for the amphipod Hyalella azteca and the midge Chironomus tentans. An interlaboratory evaluation of method precision was performed using a group of seven to 10 laboratories, representing government, academia, and environmental consulting firms. The test methods followed the EPA protocols for 4-d water-only reference toxicant (KCl) testing (static exposure) and for 10-d wholesediment testing. Test sediments included control sediment, two copper-containing sediments, and a sediment contaminated primarily with polycyclic aromatic hydrocarbons. Reference toxicant tests resulted in H. azteca and C. tentans median lethal concentration (LC50) values with coefficents of variation (CVs) of 15.8 and 19.6%, respectively. Whole sediments which were moderately contaminated provided the best estimates of precision using CVs. Hyalella azteca and C. tentans tests in moderately contaminated sediments exhibited LC50 CVs of 38.9 and 13.5%, respectively. The CV for C. tentans growth was 31.9%. Only 3% (1 of 28) of samples exceeded acceptable interlaboratory precision limits for the H. azteca survival tests. No samples exceeded the intralaboratory precision limit for H. azteca or C. tentans survival tests. However, intralaboratory variability limits for C. tentans growth were exceeded by 80 and 100% of the laboratories for a moderately toxic and control sample, respectively. Interlaboratory variability limits for C. tentans survival were not exceeded by any laboratory. The results showed these test methods to have relatively low variance and acceptable levels of precision in interlaboratory comparisons.

History and sensitivity comparison of two standard whole-sediment toxicity tests with crustaceans: the amphipodHyalella aztecaand the ostracodHeterocypris incongruensmicrobiotest

“…A second edition was published 6 years later, which described methods for evaluating survival after 28, 35 and 42 days, growth after 28 and 42 days, and reproduction during a 28-to 42-day period (USEPA, 2000). Burton et al (1996) reported and discussed in detail two ringtests organized by the US EPA in 1993 on the H. azteca assay, namely a 96-h test on a "water-only" reference chemical and a 10-day "whole-sediment" test, both of which involved 10 participants. In 1996/1997 the USEPA coordinated a second series of round-robin tests and reported the results of 10-day assays with survival as effect criterion, and of "long term" (28-day) tests based on survival and growth (USEPA, 2000).…”

“…The authors concluded that the case studies "demonstrated the robustness of the methods for successfully conducting toxicity tests with H. azteca". Burton et al (1996) gave a table on the inter-laboratory precision of the survival values for the 10-day H. azteca toxicity tests performed in 1993 by the USEPA (USEPA, 1994) with four sediments. The mean percentage survival was quite different in the four sediments, ranging from 3.3% to 94.5%.…”

A Re‐Evaluation of Chironomid Deformities as an Environmental Stress Response: Avoiding Survivorship Bias and Testing Noncontaminant Biological Factors

“…In addition, other potentially deformity‐inducing stress factors are yet to be laboratory tested. Factors such as larval density (Boglione et al ), developmental rates (Reimer et al ), dietary constituents (Cahu et al ), and pathogens (Johnson et al ) have demonstrated deformity‐inducing effects in other taxa, and are worth further consideration. Developmental rates may be of particular interest, given the faint effects suggested in our nutritional and developmental tests.…”

An interlaboratory comparison of sediment elutriate preparation and toxicity test methods

“…Overall, the interlaboratory elutriate tests demonstrated substantial agreement and similar sensitivity among both test species in the sediment samples tested. Burton et al (1996) have noted that all methods have inherent variability that must be taken into account when interpreting test results. The methods used in this study did not always find toxicity at the same sites, indicating that the elutriate preparations, storage times, and subsequent bioassay tests had built-in biases.…”