USGS, Great Rivers CESU Grant: Refinement of Hyalella azteca Culture and Toxicity Testing Protocols

The goal of this research will be to refine methods for laboratory culture and toxicity testing of H. azteca. Hyalella azteca is a widely used test organism for a variety of studies of chemical toxicity in both water and sediment. While several past studies have focused on developing appropriate test and culture conditions, and several standard methods exist, there remain some unresolved issues that have, in some instances, been suspected of potentially influencing results of toxicity tests conducted with Hyalella (USEPA 2000, ASTM 2009). Recently, the USEPA’s draft criterion for ammonia did not include toxicity data for Hyalella in the core data set because of concerns surrounding the appropriateness of test conditions in some studies, and the potential influence of water quality (chloride, in particular) on organism performance (Dave Mount, USEPA, Duluth MN, personal communication). Moreover, standard methods for conducting sediment toxicity tests with Hyalella recommend against use of reconstituted water as a source of overlying water due to inconsistencies in performance of Hyalella in reconstituted waters (USEPA 2000, ASTM 2009). Because Hyalella is not only widely used to assess water or sediment quality, but has a number of desirable characteristics as a test organism, it is important to many programs that test protocols are available that can assure the reliability of toxicological data generated with this species.

Issues potentially affecting test outcomes include, but are not limited to, the influence of culturing or toxicity testing conditions (water quality, food and substrate) and genetic strain. For example, some laboratories have been able to culture and test Hyalella successfully with so-called reconstituted “Smith water” (Smith et al. 1997) while others have not, or may have better success with other waters, such as so-called “Borgmann water” (Borgmann 1996) or natural waters (or modifications thereof). It is possible that water suitability has some interaction with the genetics, diet, or acclimation history of organism stocks used by individual laboratories, or to acclimation of laboratory cultures to particular water chemistries. Standard methods require that a laboratory demonstrate acceptable survival, growth, and reproduction of test organisms in the exposure water (USEPA 2000, ASTM 2009). Importantly, certain waters used by some laboratories may not generally support good long-term survival, growth, and reproduction of Hyalella, and this may have important implications for evaluating the suitability of Hyalella toxicity data for use in ecological risk assessment and regulatory decision making.