The B.C. Acid Mine Drainage Task Force requested a complete review of the literature available on
biological monitoring techniques related to heavy metals in aquatic environments. The review
emphasizesa conceptualf ramework for organization of the various, available biochemical, population
and community indicators. This framework allows for the future incorporation of new approaches.
Few attempts were made to summarize the results found by various research teams; it was more
important to determine that a change could be detected than to detail any controversy concerning the
direction of that change.
This review provides the AMD Task Force with details of the wide range of available indicators.
Many of these techniques have not been used specifically for examining the impacts of acid mine
drainage, but there exist no a priori reasons why they should not be valuable as indicators of the
impacts of AMD. Use of a battery or suite of biological assessmentte sts which assessre sponsesa t
the levels of individual, population and community is strongly recommended; no one method or level
of examination will provide all the required information. Biological indicators at all levels of
organization are just that -indicators- and they require, for maximum utility, supporting data from
analyses of tissue and environmental levels of contaminants, information about the history of
exposure of the organisms to contaminated habitats, and some understanding of the vulnerability of
the species to the particular contaminants.
Ecosystem health can be assessedb y monitoring in two ways: a “bottom-up” or a “top-down”
(reductionist) approach( Figure El). Both approachesh ave advantagesa nd disadvantages.R esponses
linked to detoxification processes (e.g., induction of MFOs in the case of selected organic
contaminants, and metallothionein induction in the case of selected heavy metals) have a good
conceptual basis for efficacy, since early changes in detoxification indices can generally be expected
to be quite sensitive and precede the onset of more serious pathology at cellular and tissue levels of
biological organization. Although cellular and biochemical measurements can be used as indicators
of toxicant impact, and for helping to unravel the mechanism of effect, the significance of effects
is best determined at higher levels of integration. It is often suggested that changes in simple
biochemical/physiological responses may be useful for predicting the impacts of pollutants at
population and community levels of biological organization. However, there are serious conceptual
constraints to this approach. It seemsl ikely that such simple responsesc an go no further than serving
as early warning systems for delineating potential impact zones. Conclusions about cause and effect
require demonstration of the source and pathway of impact, and a thorough knowledge of the
biological behaviour and variability within a system. As a general rule, physicochemical criteria have
probably been used with the least success in the long term management and conservation of natural
ecosystems. Therefore, it is not advisable to regulate solely based on physiological changes in algae,
invertebrates or fish.
The top-down approach initially monitors at the population or community level. Although there is
a time lag associated with changes at this level of organization, the impacts have the advantages of
integrating responses over a considerable period of time, and being relatively slow to reverse.
Regardlesso f the approach taken, most improvements in monitoring and assessmenpt rograms have
been related to the development of a comprehensive, multidisciplinary approach to problem-solving.
No single approach to the problem of biological effects monitoring is fully satisfactory. Some
methods are more useful than others, but the greatest insights are provided by multi-disciplinary
efforts.
The best understanding of the effects of acid mine drainage will be reached through a progression
of studiesf rom the community level through to the level of biochemical responsesw ithin individuals.
The disadvantageso f many community and population methods, which include poor specificity and
obscure dose-response relationships, can be addressed by follow-up testing involving the use of
appropriate biochemical tests. A key factor becomes the identification of which biochemical tests
are appropriate for use.
The most promising and proven biological monitoring techniques include the following:
- Benthic community responsesh ave been well described for acid mine drainage, and should
be the level at which preliminary measurements are conducted. Follow-up testing should
involve an assessmenot f the consequenceso f a change in benthic communities for resident
fish populations. - Growth and reproductive parameters of fish populations are easily measured, and should be
recorded during preliminary evaluations of impacts. These findings can be used to design a
more complete, detailed monitoring program once the degree of impact has been established.
Most morphological parameters are easily recorded, and should be monitored when other fish
population data are being collected. - Survival should only be measured once evidence designating a zone of impact is available.
This evidence would be composed of clear changes in benthic communities, absence of
species or decreased performance of fish populations within the impact zone. The testing
should be designed to provide information on cause and effect relationships or the impact
mechanism related to local conditions. - Other changes at the individual, biochemical level are valuable components of many studies,
and are extremely valuable for examining for the mechanism of disruption. The selection of
biochemical indicators should be based upon the mechanism of toxic action. - Measurements of gill histological changes are valuable, and have been linked to changes at
the organismal level. Estimates of biochemical parameters of growth should be restricted to
studies where an impact on growth has been demonstrated at the level of the whole organism.
Haematological parameters should only be used if there is a priori evidence that impacts on
blood constituents are expected. Some blood assays, such as the Na’ loss bioassay, can be
used to indicate potential problems during caged fish bioassays. Other blood parameters (K’
and Cl) can be useful if combined with other indications of effects and relevance to whole
organism responses. Bone metal levels can be used to indicate chronic exposure levels and
gill, liver or kidney levels to illustrate recent, metabolic activity.
It is essential to relate changes in the fish and benthos to changes in the water quality parameters.
Suitable parameters include temperature, turbidity, chlorophyll a, dissolved oxygen, nutrient
concentrations, pH, sulphates, conductivity, hardness and metal concentrations.
The future objectives of the B.C. Acid Mine Drainage Task Force are to examine the impacts of acid
mine drainage and to investigate whether water quality objectives are protective. These objectives
can be met by implementing a tiered testing approach which utilizes the biomonitoring techniques
recommended herein.
