14 - Effects of Toxic Chemicals and Other Pollutants on Aquatic Ecosystems

Abstract

This chapter discusses some general concepts of toxicology, causes and effects of pollution by inorganic and organic contaminants, and thermal pollution and mitigating solutions. Bioassessment protocols can be used to assess the impacts of pollutants and other habitat alterations on aquatic communities. Acid rain has major effects on biological systems ranging from altered microbial activity to the ability of fish to survive and reproduce. Acidification of aquatic ecosystems impacts all aquatic organisms. One of the basic ecosystem influences of acidification is the lowered rate of decomposition mediated by microbes. Algal populations are influenced by acidification. Diversity of plants and animals also decreases as aquatic systems become more acidic. A wide variety of metals and some other inorganic materials act as toxic pollutants in aquatic ecosystems. Metals can bioaccumulate in many organisms, and can be bioconcentrated in trophic food chains. Bioconcentration has led to problems such as excessive lead contamination of fish. Atmospheric deposition and industrial waste releases, particularly mining, are common sources of metal contamination. Such mining activities have had extensive negative impacts in some aquatic habitats. More than 10,000 organic compounds are discharged by humans into aquatic habitats, including pesticides, oil, and materials in urban runoff. Suspended solids can cause harm to aquatic organisms. Thermal pollution can cause shifts in community structure. This may allow for establishment of exotic species and local extinction of native species.