Toxicity Tests   

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). 

Site-Specific Toxicity Tests 

Site-specific toxicity tests may be conducted using samples derived from the site (ex situ tests), or by placing test organisms in enclosures at the site (in situ 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.