Chapter 15: Aquatic Toxicology
John B. Sprague
This chapter is intended primarily as a user’s guide for interpreting and applying results in aquatic toxicology. Much of the chapter is guidance for evaluating procedures used in tests. There are thousands of results from aquatic toxicity tests in the published literature, and not all of them are based on good procedures. A person who actually wished to do a toxicity test would need further details, and appropriate references are given in Section 15.3 and elsewhere.
This chapter emphasizes toxicological studies on fish. However, there now is considerable emphasis on testing invertebrates (which often are more sensitive to toxicants than fish, and more variable in response) and to some extent algae and other plants (Stephan et al. 1985) because communities and ecosystems must be protected from toxicants, not just a single group such as fish. Many of the items covered for fish also apply to other organisms, but some reference will be made to particularly advantageous tests with invertebrates. This chapter also emphasizes applied toxicology and whole-organism effects. Sections 15.5.6 to 15.5.8 assess some within-organism effects without attempting to cover the myriad of specific biochemical and other techniques. There are important goals for such research (Section 15.5.6), but available data indicate that concentrations of toxicant causing meaningful within-organism changes are no lower than, and are often much higher than, those that cause sublethal whole-organism effects. Often there is a question as to whether a biochemical change is a deleterious one or merely an adaptation within the usual range of the organism; the importance of the change can be ascertained only within the context of the whole organism.
The major reason for carrying out toxicity tests with fish and other aquatic organisms is to determine which concentrations of a substance are harmful to the organisms and which have no apparent effect. From the results, a toxicologist can recommend maximum concentrations for the well-being of aquatic organisms, engineers can design treatment systems to achieve desjred levels, and fisheries managers can evaluate chemical measurements in local bodies of water. All the data provided by toxicity tests may be assembled to derive water quality criteria, which should be scientifically sound numbers relating concentration to effect. The criteria may be used to create water quality standards or objectives (see terminology in the next section).