Nutrient Cycling in Freshwater Ecosystems

Abstract

Flaws in logic or methodology have often caused erroneous conclusions to be drawn from chemical experiments in fresh water. Some examples follow. The acid-molybdate method was found to greatly overestimate phosphate concentrations in many lakes. Phosphorus was found to be hydrolyzed from organic substances in filtered lake water by the acid molybdate reagent. The 1 4 C bottle bioassay technique is often misapplied to management questions. It was demonstrated that while lake 227 became eutrophic as the result of additions of phosphorus and nitrogen bioassays indicated that carbon was limiting throughout much of a typical day. Carbon limitation was the result of, rather than the cause of, eutrophication. In spite of low carbon concentra- tions, enough 002 was able to invade the lake from the atmosphere to allow algal blooms to develop. Comparisons with data from the Laurentian Great Lakes indicate that there is no possibility of car- bon limitation being of any significance to eutrophication manage- ment in those waters. INTRODUCTION