Although limnology is a young discipline, it has, over the past century, experi enced marked growth. Its early descriptive period was a long one, given the enormous diversity of biota and environments in freshwater ecosystems. With the development of quantitative techniques came the ability to measure production rates and other parameters and to demonstrate the effects of nutrient limitation and predation on productivity and energy flow. As understanding of these phenomena grew, so too did our appreciation of the many complex chemical interactions among the biotic and habitat components of...