PRINCIPLES OF ENVIRONMENTAL TOXICOLOGY AND CONTAMINATION (PART II)

Table of Contents

1. Index
2. UNIT 5 - Transport and fate of contaminants in the environment
3. UNIT 6 - Principles of toxicokinetics and toxicodynamics
4. UNIT 7 - Biotransformation
5. UNIT 8 - Toxicity Testing
   1. Introduction
   2. Dose-response relationships
   3. Test design and test species
   4. Indicator species
   5. Model organisms
   6. Biomarkers and monitoring studies
6. Glossary of key terms associated with environmental toxicology

Indicator species

An indicator species is any biological species whose presence, absence or abundance reflects a specific environmental condition, such as pollution, species competition or climate change. Species that react positively to environmental contamination or whose behaviour suffers a modification compared to a normal status can also be considered indicator species. Hence, indicator species can be among the most sensitive species in an ecosystem and sometimes act as an early warning in biomonitoring studies (e.g. sentinel species).

Other indicator species are considered, attending their role in the ecosystems. Organisms such as oysters and mussels have been extensively used as indicator species in marine and estuarine environments due to their well-documented feeding habits, stationary condition and their important role as integral parts of the food chain in the ecosystem. A considerable amount of contaminant concentrations are found in the sediments of marine and estuarine environments. Once in suspension, contaminants may be transported by tidal currents to other parts of the estuary and possibly to the ocean. As mussels and oysters are filter feeders, contaminant uptake occurs by ingestion of particulates in the water column. Hence, sediment suspension takes an important role in the bioaccumulation process which aids the evaluation of possible adverse biological effects of sedimentary contaminants in marine and estuarine environments.