THE STOICHIOMETRY OF CARBON, NITROGEN, AND PHOSPHORUS IN PARTICULATE MATTER OF LAKES AND OCEANS

The mean carbon, nitrogen, and phosphorus contents of particulate mate rial for 51 lakes or lake basins, extending from arctic to tropical cl imatic regions, including small lakes as well as the largest lakes in the world, indicate that Redfield ratios are the exception rather than the rule in freshwater. The C : P and N : P ratios are more variable for lake particles but generally higher than marine particles, and the mean molar C : N, C : P, and N : P ratios are substantially higher th an the Redfield ratio of 106 : 16 : 1. On average, lower C : N, C : P, and N : P ratios occur in subarctic lakes while higher ratios occur i n the tropics and in temperate, oligotrophic lakes on the Canadian Shi eld. In shield lakes with long residence times (>6 months) the high ra tios of C : N, C : P, and N : P do not originate from streamborne or a tmospherically deposited particles but arise from in-lake processes. R egression analysis demonstrates that small lakes are generally more N and P deficient than large lakes. In freshwaters, particulate composit ion ratios imply that a wide variety of conditions exists in lakes, in cluding N and P deficiency, as well as N and P sufficiency. In the Exp erimental Lakes Area of Canada, independent physiological nutrient sta tus indicators generally agree with the status indicated by seston rat ios. The relative uniformity of marine C : N : P composition (compared to lakes) at the Redfield ratio suggests that marine plankton cannot be as severely, or as frequently, limited by N and P as lake plankton. Consequently, the paradigm of N limitation in the oceans requires qua lification. Based on particulate composition, it is more correct to sa y that ocean plankton is not as N and P deficient as lake plankton.