Sediment ecotoxicology—Current research on laboratory methods: An introduction

In the late 1980s and early 1990s government agencies began using toxicity testing to reduce the input of toxic chemicals into aquatic ecosystems from industrial discharges through programs such as the US Environmental Protection Agency's (USEPA's) Whole Effluent Toxicity testing program, Environment Canada's Metal Mining Effluent Regulations and Pulp and Paper Effluent Regulations, and the Ontario Municipal Industrial Strategy for Abatement. To do this successfully, agencies used a combination of chemical characterization and impairment of aquatic organisms as measured in ecotoxicity tests 1-4. To be successfully incorporated into a regulatory framework and useful tools in monitoring and enforcement activities, ecotoxicity test methods had to be robust, repeatable, and relatively simple to conduct and understand—in other words, “standardized” test methods. The obvious success of using these methods to reduce toxic industrial discharges has led to ecotoxicological testing of water, soils, and sediments becoming a critical component of decisions on product registration, litigation in environmental offenses, allocation of remediation resources, forensic investigations of source track-down, impact assessments of navigation channel dredging, and monitoring of the effectiveness of cleanup activities and natural recovery. Uncertainty is an uncomfortable reality of any risk assessment; however, it is paramount to try to reduce uncertainty and thereby increase public and stakeholder confidence in potentially costly decisions made using data from ecotoxicological tests. Although high confidence in chemical analytical test results is easy to achieve with technical analytical quality-control procedures, the more ecologically relevant biological testing procedures can be influenced by many biological and chemical processes that are poorly understood or difficult to control. The value of standardized methods published by standards organizations (such as ASTM International, the USEPA, Environment Canada, and the Organisation for Economic Co-operation and Development) is to provide procedures that, when properly followed, ensure consistent results independent of where and by whom the test was conducted. The effluent toxicity test methods listed above have undergone continual refinement and have been standardized and updated to improve on the repeatability and reproducibility of the test results, and many other standardized test methods are available. Standardized methods are also available for conducting laboratory tests to assess the toxicity and bioaccumulation of sediment-associated contaminants on fish and aquatic invertebrates (see Burton 5 for a thorough review of the history of sediment toxicity assessment). The complexities associated with understanding the bioavailability and toxicity of contaminants in the vast variety of sediment types present in the environment creates an even bigger challenge for method development that aims to increase repeatability and confidence in sediment toxicology and bioaccumulation test methods. For more than 30 yr, short-term sediment toxicity test methods have been developed and refined to assess survival and growth with sediment organisms; however, methods to test sublethal chronic effects such as reproduction impairment as a result of exposure in both water and sediment are in development to allow for increased understanding of risk and increased ecological protection. The purpose of this special section, “Sediment Ecotoxicology—Current Research on Laboratory Methods,” is to showcase research efforts to understand culturing and testing factors that influence the outcome of laboratory-based acute and chronic toxicity, bioaccumulation, and toxicity identification evaluation (TIE) tests with sediment organisms. In the first 3 articles (Soucek et al. 6, Kennedy et al. 7, and Ivey and Ingersoll 8), the authors thoroughly investigated the influence of food and water in culturing and testing on organism reproduction, sensitivity, and method performance with the freshwater amphipod Hyalella azteca. Although these articles revolve around testing in a water-only system, the lessons learned can easily be transferred to sediment testing with Hyalella azteca. In the fourth article (Taylor et al. 9), the authors detail the internal method validation assessment of the ability of Environment Canada's proposed 42-d Hyalella azteca reproduction test method in sediment to meet control validity criteria. In the fifth (Ivey et al. 10) and sixth (Watson-Leung et al. 11) articles, the authors report the results of interlaboratory testing (with Hyalella azteca and the burrowing mayfly Hexagenia spp.) and demonstrate the value of cross-laboratory performance comparisons to assist with revising standard methods to include key method requirements that influence test outcome. In the final article (Bailey et al. 12), the USEPA TIE procedure was applied, and the robustness of the standard TIE method was assessed using the marine amphipod Leptocheirus plumulosus. The authors identify the complexities associated with sediment contamination and toxicity. Through description of a quantification procedure, the article demonstrates that the TIE method is robust for identifying the cause and level of toxicity in sediments with multiple sources of toxicity. Together, these articles further our understanding of the reliability and sources of uncertainty in methods used to assess the effects of sediment toxicity on aquatic organisms. A sincere thank-you goes to C. Ingersoll, not only for his contribution to the development and coordination of this special section on sediment ecotoxicology but also for his immeasurable influence and contributions to the advancement and promotion of toxicological method development and improvement over the course of his career. Trudy L. Watson-Leung Environmental Sciences and Standards Division, Laboratory Services Branch, Ontario Ministry of the Environment and Climate Change Toronto, Ontario, Canada Christian Picard Smithers Viscient Wareham, Massachusetts, USA