Introduction: Natural and cultural eutrophication (enrichment with nutrients) frequnetly results in excessive algal growths thereby reducing the beneficial uses of surface waters (Hasler, 1947; Thomas, 1955, Edmondson et al., 1956, Oswald and Golueke, 1966, Skulberg, 1967, Mackenthun et al., 1968, Goldman and Armstrong, 1969, McGauhey et al., 1968,1969, 1970a, 1970b). Recent reviews emphsize that the prevention of further reduction in the quality of water resources requires the implementation of effective control measures (Goldman, 1965, Steward and Rohlich, 1967, Middlebrooks et al., 1969, Rohlich, 1969). Effective control of cultural eutrophication must involve the manipulation of those factors which affect algal growth, i.e. light, temperature, nutrients, mixing predation, etc. (Toerien et al., 1970). Because at the present time man can only effectively control the discharge of nutrient concentrations into aquatic systems, most past and current research on the remediation of eutrophication effects has been concerned with nutrient control. The cost of removal (or exclusion) of specific nutrients varies, so from an economic standpoint it becomes important to indentify which nutrients limit algal growth for a given situation. Algae require carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, magnesium, iron, potassium, various other cations, and anumber of trace elemtns to carry out the metabolic processes necessary for growth. Only a few of these elements can be removed from water through treatment at this time. Althrough Goldman (1960) and Skulberg (1967) have implicated magnesium, iron and molybdenum, and other trace elements as limiting factors for algal growth in some waters, most attention has been directed towards nitrogen and phosphorus as limiting nutrients. Several reasons for this interst in nitrogen and phosphorus follow: (1) Nitrogen and phosphorus are relatively major constitutents in algae; a typical stoichiometric formula for algal biomass being C106H181O45N16P (McCarty, 1970); (2) Geochemical considerations suggest that phosphorus is probably the most frequently limiting nutrient (Hutchinson, 1957); (3) The considerably detailed information on the behavior of nitrogen and phosphorus in nature (Hutchinson, 1957, Task Group 2610P (AWWA), 1967); (4) The relative ease and familiarity of chemical analysis (e.g. Amer. Publ. Health Assoc., 1965) at the relatively high concentraions observed in waste waters (McGauhey, 1968); (5) the vast amount of research performed on the physiological and biochemical utilization of nitrogen and phosphorus (e.g. Fogg, 1959, Lewin, 1962, Kuh, 1968); (6) at least for phosphorus, the relative ease with which it can be removed from waste waters by chemical treatment (Wuhrmann, 1957, Rohlich, 1961). Because phosphorus can be removed relatively easily in both economical and technical terms (e.g. Cult and Moyer, 1969) and because it has been considered to be the most probable limiting nutrient in most natural waters, proposals for constructin tertiary treatment plants for removing phosphorus from waste waters, elimination of phosphate builders in detergents, and limitations on the use of phosphorus fertilizers have been advanced as aids in controlling eutrophication. Recently the concept that phosphorus is the most probable limiting nutrient in natural waters habeen questioned (Legge and Dingledein, 1970) and several investigators have suggested that carbon is really the most important limitng nutrient in natural waters (lange, 1067, Kuentzel, 1969, Kerr et al., 1970, King, 1971). These considerations have now entered the realm of controversy (Kuentzel, 1969, 1970, Legge and Dingledein, 1970, Sawyer, 1970, Shapiro, 1970, Abelson, 1970, Bowen, 1970, Likens, 1971). The implication of carbon as being a major factor in controlling cultural eutrophication has significant consequences. Currently removal of phophorus from detergents has been advocated (Environmental Science and Technology, 1970, Dawson, 1970). The economic aspects of phosphoros removal and replacement with other materials for the consumer and manufacturer and the environmental effects of possible replacements (e.g. substitutes similar to the recently banned nitrito-triacetic acid (NTA)) on aquatic ecosystems have not been evaluated. Therefore, serious questioning of the role of phosphorus in the eutrophication of natural waters may be warranted. However, the possible role of other factors which can limit algal populations should be considered in light of the extensive literature which exists on the subject of algal growth. It is the goal of this review to clarify and obtain a perspective on the role of carbon in controlling algal growth in natural waters. information on carbon cycling and metabolism, inorganic carbon chemistry, algal utilization of carbon, and concepts of nutrient limitations will be discussed and reviewed to gain this perspective. This information will provide for a more complete understanding of the role of carbon in eutrophication.
Goldman, Joel C.; Porcella, Donald B.; Middlebrooks, Joe E.; and Toerien, Daniel F., "The Effect of Carbon on Algal Growth--Its Relationship to Eutrophication" (1971). Reports. Paper 462.