Aquatic Sciences Meeting, Albuquerque 2001

CS25 Organic Carbon Dynamics

Date: Wednesday, February 14, 2001, Time: 2:30:00 PM

Location: Acoma/Zuni/Tesuque

Pace, M, L, Institute of Ecosystem Studies, Millbrook, USA, pacem@ecostudies.org

Cole, J, J, Institute of Ecosystem Studies, Millbrook, USA, colej@ecostudies.org

SYNCHRONOUS VARIATION AMONG LAKES IN DISSOLVED ORGANIC CARBON

Dissolved organic carbon (DOC) concentration is a key feature of aquatic systems. Variation in this large pool is important to carbon cycling as well numerous physical, chemical, and biological processes associated with DOC. There has, however, been limited analysis of factors related to DOC variation especially at longer temporal scales as well as among ecosystems. We present results of a long term study of DOC variation in 20 lakes that reveals significant temporal variation of DOC within lakes as well synchronous variation among lakes. We made monthly measurements during summer of DOC, color (absorbance at 440 nm), total phosphorus (TP), and chlorophyll. The study lakes varied widely in DOC (O.2-1.8 mM) while being located in close proximity within the 3000 ha of the University of Notre Dame Environmental Research Center. We observed significant seasonal and interannual variation in DOC. For example, several lakes had a 1.5-fold difference in the range of annual mean DOC. Both DOC and color varied synchronously as reflected by positive correlations between time series. This synchrony indicates a common response to climatic conditions. DOC and color declined significantly in lakes during drought and increased during wet periods. TP and chlorophyll did not vary synchronously reflecting, as others have observed, greater regulation by internal processes. The magnitude of variation in DOC and color was sufficient to result in large changes in the light penetration as well as likely changes in the contributions of allocthonous carbon to lake metabolism.

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Aquatic Sciences Meeting, Albuquerque 2001

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