Dissolved organic carbon (DOC) and its bioavailability in Lake Esrum, Denmark

摘要

The standing stock of organic carbon is in most lakes dominated by dissolved organic carbon (DOC) of either allochthonous or autochthonous origin. Bacteria efficiently keep easily accessible dissolved compounds at very low concentrations; thus, compounds with long turnover times normally dominate the DOC pool. However, between 10-25% of the standing stock is bioavailable (BDOC) over time scales of days to weeks (Sondergaard & Middelboe 1995). The most recent review on DOC lability, Del Giorgio & Davis (2003), concluded a higher percentage of lake DOC was labile compared with river and marine samples. They also observed a systematic difference in degradation kinetics among systems. Marine waters have very high initial degradation rates compared to lakes and rivers. Differences in BDOC concentrations and degradation kinetics among systems are difficult to explain, but likely explanations are the origin and age of DOC (Del Giorgio & Davis 2003). Very few studies have covered seasonal and spatial developments in DOC lability, so it is not known how much within system variability affects cross-system analyses. It was the purpose of this study to follow the seasonal pattern of DOC and its degradability in a dim-ictic, temperate lake dominated by autochthonous DOC.