Nutrient - Primary Production Relationships in Central Lake Erie: A Simple Correlation Approach

GLOOSCIIENFVO, w. A. Nutrient-primary production relationships in central Lake Erie: A simple correlation approach. Ohio J. Sci. 75(5): 251, 1975. Correlation coefficients were determined between primary production, phytoplankton biomass as chlorophyll a, temperature, and forms of N, P, and Si in Lake Erie during 10 cruises between April and December, 1970. The Central Basin was emphasized due to too few stations in the Eastern and Western Basins for significant statistical analyses. Primary production was significantly affected by nutrients in the summer when concentrations in the water were quite low. Temperature appeared to be of secondary importance. Chlorophyll a rarely correlated with any of the measured parameters. Dissolved inorganic nitrogen (NO^ + NO^) appeared to be more limiting in the summer than phosphorus. A highly significant positive relationship between particulate phosphorus and primary production was found on all cruises suggesting the use of the measurement of particulate phosphorus as a possible biomass indicator. Lake Erie is well-known to both the layman and limnologist as a highly productive ecosystem exhibiting the symtoms of cultural eutrophication, especially in its Western Basin. Nutrient inputs, mainly from U.S. domestic and industrial sources, have been suggested as the cause of this high production (IJC, 1969). The key nutrient involved in such problems has been felt to be phosphorus (see Vollenweider et al, 1974), and this relationship has been the basis of phosphorus control of effluents as set forth in the Canada-U.S. agreement of 1972. Much controversy on the role of Manuscript received April 18, 1975, revised August 25, 1975 (#75-23). phosphorus as a "limiting nutrient," came out in the early 197()'s culminating in a special symposium entitled "Nutrients and Eutrophication: The limitingnutrient controversy" (Likens, 1972). This paper will attempt to investigate the interrelationships between selected environmental parameters, both nutrients and temperature, and observed patterns of both algal biomass as measured by chlorophyll a and primary production in Lake Erie. Temporal and spatial distributions of these biological parameters have been previously discussed by Glooschenko et al (1974a, b) and temperature and nutrients by Gachter et al (1974). It is the opinion of the author that the word "limiting factor" is a highly confused term in the literature due to arguments over whether there can be only one limiting factor in the sense of Leibig's "Law of the Minimum" (Hutchinson, 1973; O'Brien, 1972) or several simultaneous limiting factors. At a given time in Lake Erie, the phytoplankton consist of many taxa of algae, each with different physiological responses to environmental parameters such as light, temperature, individual nutrients, and potential inhibitors such as trace metals. The author, therefore, feels that in utilizing integrated terms such as biomass and production the idea of a single limiting factor is hard to apply.