Using an interlaboratory study to revise methods for conducting 10‐d to 42‐d water or sediment toxicity tests with Hyalella azteca

Chris D. Ivey, Chris G. Ingersoll, William G. Brumbaugh, Edward J. Hammer, Dave R. Mount, J. Russell Hockett, Teresa J. Norberg‐King, Dave Soucek, Lisa Taylor

Studies have been conducted to refine USEPA, ASTM, and Environment Canada standard methods for conducting 42-d reproduction tests with H. azteca in water or in sediment. Modifications to the H. azteca method include better defined ionic composition requirements for exposure water (i.e., >15 mg/L of chloride and >0.02 mg/L of bromide) and improved survival, growth and reproduction with alternate diets provided as increased rations over time in water-only or whole-sediment toxicity tests. A total of 24 laboratories volunteered to participate in an inter-laboratory study evaluating the performance of H. azteca in 42-d studies in control sand or control sediment using the refined methods. Improved growth and reproduction of H. azteca was observed with 2 alternate diets of (1) ramped diatoms (Thalassiosira weissflogii) + ramped Tetramin or (2) Yeast-cerophyl-trout chow (YCT) + ramped Tetramin, especially when compared to results from the traditional diet of 1.8 mg YCT/day. Laboratories were able to meet proposed test acceptability criteria (TAC) and in most cases had lower variation in growth or reproduction compared to previous inter-laboratory studies using the traditional YCT diet. Laboratory success in conducting 42-d H. azteca exposures benefitted from adherence to several key requirements of the detailed testing, culturing, and handling method. Results from this inter-laboratory study are being used to help revise standard methods for conducting 10- to 42-d water or sediment toxicity exposures with H. azteca. This article is protected by copyright. All rights reserved.