ABSTRACT
Continental aquatic ecosystems, coastal lagoons, and estuaries are subject to several environmental problems and impacts as a consequence of human activities. These impacts can be permanent and cumulative, periodic, or as a pulse due to accidental occurrences such as oil spills or discharges of contaminants from industrial and agricultural activities. There are two main sources of impacts: nonpoint sources, originating from several processes in the watersheds, or point sources such as effluents of industries or urban discharges of insufficiently treated domestic wastewater. Another nonpoint source of impacts is the atmospheric contribution as particulate matter or dissolved substances in rainwater. For example, acid rain originates from the processes of accumulation of H2S or SOx in the atmosphere (Jørgensen et al. 2005). Besides the intensification of the sources and the magnitude of impacts on continental aquatic ecosystems, coastal lagoons, and estuaries, it is fundamental to understand the fate of the pollutants and contaminants in the aquatic ecosystems including their possible accumulation in the food chain (see the use of mass balances in Chapter 9 to quantify this important process). It is also relevant in the identification and study of impacts to clarify effects on the ecosystem services. For example, the eutrophication or toxic metal contamination can affect water supply and other (multiple) uses of water. The impact on ecosystem services has indirect or direct effects on the regional economy; for example, by accumulation of toxic metals in the sediment or in the water, fisheries may be affected. Recreation and tourism, which are, in many regions of the world, a major source of economic and social development, may also be impaired by eutrophication. For loss of ecosystem services and general degradation of rivers, reservoirs, estuaries, and coastal waters see Straskraba and Tundisi (1999).
