Initial expense for such a testing approach will be very high. As the data base is expanded, however, it may become possible to reduce the number of necessary tests to those few that consistently distinguish community stress effects. Currently such a reduction is being made on the basis of assumptions and theoretical arguments, rather than on the basis of accumulated scientific data. Therefore, the accuracy of such tests now in use in measuring ecosystem stress response can be questioned.

Finally, the major advantage in conducting simultaneous field and microcosm comparison tests may go well beyond the establishment of a set of best tests for ecosystem stress response. A high correlation between microcosm and field responses would allow effluent hazard evaluations to be made with the least amount of risk.