There are numerous methods manuals, standard guides, and procedures
for conducting toxicity tests. Environment Canada’s ERA framework
(1994; Table 6.3). Table 6.3 provides a particularly useful summary of the toxicity tests that
might potentially be used for toxicity assessment at contaminated sites. However, it is important to remember that toxicity testing
only serves to model the field situation and is not truly
representative of the dynamics of populations and communities
(Environment Canada 1994).
tests may be conducted using samples derived from the site (ex situ
tests), or by placing test organisms in enclosures at the site (in
tests), or by measuring toxicity on populations of indicator organisms
present at the site (field tests).
Toxicity data derived from
site-specific tests are more relevant than standardised laboratory tests
because they take into account modifying factors such as mixtures of
contaminants, and soil characteristics that can influence
bioavailability such as organic matter. However, single or mixed
chemical laboratory tests may be necessary if site-specific toxicity
data are not of a high quality or if they give ambiguous results.
In situ testing using caged organisms has been
successfully used in New Zealand receiving waters to assess impacts on a
number of fish and invertebrate species, including eels and bivalve
molluscs. Organisms may be deployed for extended periods to
measure both the bioavailability and uptake of contaminants, as well as
their effects on organism health.
Note: Toxicity testing is a specialised field with a variety of approaches
and methods from which to chose. You may wish to approach an
organisation such as CENTOX or
NIWA for advice.
For further information read about ecotoxicity testing that has been
undertaken in New Zealand.
A list of Resources for
Ecotoxicity Testing Protocols is also provided.