The Coastal Resource Coordinator's Bioassessment Manual

HAZMAT 93-1–Bioaccumulation
do not measure the level of contaminants that are available through active uptake
mechanisms and through the ingestion of particulates, sediments, and food. Particulates
and sediments may be significant sources of contaminants for filter and deposit feeders,
respectively. Also, food is a particularly important source for those contaminants that
biomagnify. Therefore, it must be kept in mind that artificial organisms are just simplified
models of real organisms and, as such, are not able to indicate exactly what real organisms
accumulate.
Test Organism Selection
The selection of an appropriate organism, whether indigenous or transplanted, for a
bioaccumulation study is extremely important. Table 4-3 gives a list of criteria that should
be considered when selecting an organism for a bioaccumulation study. The ideal organism
should meet all of these criteria, but since bioaccumulation studies are conducted in the real
world, that organism doesn't exist. Possibly the two most important criteria are numbers 1
and 8. The test organism should be able to tolerate the expected levels of contamination
without any significant changes in its viability, including changes in its metabolic rate. Any
such changes may reduce the bioaccumulation rate. The organism should also concentrate
the contaminant or contaminants of concern. For example, while leeches meet most of the
selection criteria, they would be a poor choice of organism for PCB studies because they do
not accumulate organochlorides (Environment Ontario, 1988).
Sedentary organisms are preferred (criterion 2) because they can be associated with a
specific location and the bioaccumulation data can be related to sediment chemistry. If
biomagnification or routes of human exposure are of concern, then non-sedentary
organisms from higher trophic levels might be preferable. However, it is difficult to
associate non-sedentary organisms (e.g., fish) with specific locations and thus specific levels
or sources of contamination. If they are used, then this lack of precision should be noted.
The organism needs to be hardy enough (criterion 7) to transport to and survive in a
laboratory in case depuration before analysis is necessary; this is particularly true of deposit
feeders whose gut content could be a significant proportion of total body concentration of a
contaminant (Chapman, 1985). In the case of transplant organisms, they need to be hardy
enough to survive collecting, handling, and caging. Some organisms actively regulate levels
of certain contaminants, especially those that are also essential micronutrients. This
regulation can confound the correlation between organismal and water concentrations
(criterion 9). For example, Cu is regulated by mussels, and, therefore mussels are not a good
indicator of its bioavailability (Phillips, 1977).
4-7 November 1992