The Coastal Resource Coordinator's Bioassessment Manual

HAZMAT 93-1–Toxicity Tests
1986; Long et al., 1990; Pastorak and Becker, 1989). However, this relative sensitivity now
appears to be site or species specific (Long, personal communication). Amphipods may be
more sensitive to creosote and PAHs than the Microtox ® test (Pastorak and Becker, 1989).
The polychaete Neanthes appears to be sensitive to metals and PAHs (Johns, 1988). The
embryos and sperm cells of the sea urchin Arbacia punctulata appear to be similar to oyster
larvae in their sensitivity to metals (Nacci et al., 1986).
In general, only healthy organisms of similar size and life history stage should be used in
toxicity tests. The organism should be appropriate for the material to be tested. For
example, a planktonic or pelagic organism would be appropriate for a water toxicity test
and a benthic organism would be appropriate for a sediment toxicity test. Taxonomic
identifications of organisms must be confirmed by a qualified taxonomist.
Acute or Chronic Testing
Toxicity tests can be classified as "acute" or "chronic" tests. These terms refer to the duration
of the test with regard to the life cycle of the organism being tested, not to the endpoint of
the test. However, there is no universal agreement on the precise definition of these terms.
For short-lived organisms, for example, daphnids, choronimids, and amphipods, the
definitions are fairly straight forward and universally accepted: an acute test is one that is
completed within a small portion of the organism's life cycle, while a chronic test exceeds
at least one life cycle (Chapman, 1989). The problem with the definitions arises when longlived
organisms, such as fish, are tested. This is because it is impractical to run life-cyclelength
toxicity tests when the life cycle is a year or more. Even if the life cycle is only a few
months, life-cycle-length tests would be impractical on a routine basis. Therefore the
question is: how long must the duration of a test be for it to be considered a chronic test
when it is impractical to run it for one or more life cycles There is currently no generally
accepted answer to the question.
Endpoints
The endpoint of a toxicty test is the response of the organism that is used as a measure of
toxicity. Endpoints can be classified as "lethal" or "sublethal." The only lethal endpoint is
the death of the test organism and is reported as either percent survival or percent
mortality. Sublethal endpoints do not involve the death of the test organism but are
responses that could affect the survival of in situ populations. Sublethal endpoints include:
developmental abnormalities, behavioral changes, changes in reproductive success, and
physiological responses reflecting changes in enzyme activity and growth rates. While
3-9 August 1997