The Carbon Problem 



In the early 1970's a major controversy developed in regard to the rela- 

 tive importance of carbon, phosphorus, and nitrogen in regulating eutrophi- 

 cation. This controversy centered on a contention that carbon rather than 

 phosphorus or nitrogen limits algal productivity in many aquatic ecosystems. 

 Since phosphorus in detergents is linked to cultural eutrophication of 

 lakes and streams, the controversy became emotionally charged following pro- 

 posals to remove phosphorus from detergent formulations. Because of this, 

 the American Society of Limnology and Oceanography sponsored a special 

 symposium entitled "Nutrients and Eutrophication: The Limiting-Nutrient 

 Controversy" (Likens, 19/2). This symposium was held in February 1971 in 

 an effort to provide a clear statement on the relative importance of 

 various regulating or limiting nutrients in the eutrophication of aquatic 

 ecosystems. The papers and discussion focused not only on phosphorus, 

 nitrogen, and carbon, but also considered other nutrients and environmental 

 factors that affect eutrophication. As various ideas, views, and data were 

 openly and authoritatively debated, there emerged a general agreement that 

 phosphorus is the critical limiting nutrient in most North American lakes 

 and hence should be the center of focus for management programs. This ex- 

 pression in the published proceedings provides guidelines to the public and 

 to officials concerned with lake protection. 



Nutrient Loading 



Preventive and remedial programs based on nutrient-control measures can 

 be initiated effectively only after the origins of the nutrient supplies 

 have been determined. To obtain an accurate nutrient budget, all sources 

 must be considered, including all tributaries, industrial discharges, muni- 

 cipal discharges such as sewage and storm waters, precipitation, ground 

 water, unchanneled surface runoff, and last but not least, feedback from 

 the lake sediments. Synthesis of such a budget for even one nutrient is 

 time-consuming, difficult, and expensive. Few accurate nitrogen and phos- 

 phorus budgets exist for U.S. lakes. Of these, the phosphorus budgets are 

 generally more accurate than those for nitrogen. 



Several actions are underway to improve our understanding of the relar 

 tionship between lake loading and lake response. One program is the OECD 

 North American Project. Approximately 40 scientists from the United States 

 and Canada are collecting and analyzing limnological data from selected 

 lakes. Correlations of nutrient loading with mean depths and water-resi- 

 dence times are being examined to determine relationships of these factors 

 to the prevailing trophic level in the studied lakes. The results of this 

 study will be available soon. 



Organization for Economic Cooperation and Development. 



91 



