The seasonal cycle of inorganic carbon species in Cazenovia Lake, New York, 1977 *

SUMMARY. Spatial and temporal distributions of inorganic carbon and related ionic species (Ca2+, H+) were monitored weekly for 1 year in Cazenovia Lake, a small mesotrophic marl lake. Attendant [H2CO*3]([H2CO3] + [CO2(aq)]) and CaCO3 equilibrium conditions were determined through application of equilibrium equations adjusted for appropriate temperatures and ionic strength. A seasonal cycle was demonstrated for the inorganic carbon species which was temporally correlated to the lake's thermal and productivity cycles. Vertical homogeneity in carbonate chemistry was evident during turnover periods while dramatic differences developed between the epilimnion and hypolimnion during winter and summer stratification. The lake was supersaturated throughout the year with H2CO*3, though saturation was approached during the productive summer months in the epilimnion. The epilimnion was supersaturated with respect to CaCO3, from the start of spring turnover to the end of autumn turnover. Calcium (Ca2+) levels within the epilimnion decreased through much of the same period. Dissolution of CaCO3 in the hypolimnion is indicated by increases in Ca2+ and alkalinity as stratification periods progress. Analysis of potentially influencing factors indicates that the seasonal trends were mostly a result of CO2 metabolism. This was further supported by concurrent algal biomass and 14C uptake.