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Effluent bioassays measure the survival, growth, or reproduction of aquatic organisms exposed directly to effluents (Goulden). Effluent bioassays are frequently required by government regulation. Their advantage is that they directly measure the response of organisms to whatever mixture of materials is being released to the aquatic environment. Strictly speaking, these bioassays measure environmental performance, but they have properties more characteristic of measures of environmental condition. For example, like most biologically based measures of ecosystem condition, the test organisms respond to the complete suite of effluent components. Thus, with the use of effluent bioassays, humans need not make assumptions about the relative toxicity of different effluent components. However, it can be difficult to determine why the organisms respond as they do or even to what they are responding. Finally, as Goulden argues, the widespread use of effluent bioassays risks a sort of complacency if bioassay results are extrapolated carelessly. As Goulden explains, an effluent could damage an ecosystem even if it does not appear to be toxic in conventional effluent bioassays.
National or Regional Measurements
Natural Resource Accounting
From an environmental perspective, the widely used measure of national economic health, gross national product (GNP), has two important shortcomings: It does not include depreciation charges for depletion of the natural resources that form the basis of production, and it does not incorporate the costs of environmental externalities (environmental consequences of market transactions that are not reflected in market prices). Repetto et al. (this volume) explain that "a country could exhaust its mineral resources, cut down its forests, erode its soils, pollute its aquifers, and hunt its wildlife and fisheries to extinction, but measured income would not be affected as the assets disappeared."
Natural resource accounting methods attempt to overcome the environmental shortcomings of traditional accounting calculations (Daly and Cobb, 1989; Solorzano et al., 1991). These methods ascribe prices to various forms of environmental degradation and then add those values into conventional accounts, thereby providing more comprehensive accounts of the consequences of economic activities. Repetto et al. use a case study of Indonesia to illustrate natural resource accounting. They show that although Indonesia's GNP increased by an average of 7.1 percent per year from 1971 to 1984, the increase drops to an average of 4.0 percent per year when a few major forms of environmental depletion are factored in.
Repetto et al. further describe the insights from natural resource accounting that accrue when the method is applied to particular components of a nation's economy. They show that conventional accounting calculates the net economic