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Role of dissolved organic matter in hypolimnetic mineralization of carbon and nitrogen in a large, monomictic lake
Author(s) -
Kim Chulgoo,
Nishimura Yoko,
Nagata Toshi
Publication year - 2006
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2006.51.1.0070
Subject(s) - hypolimnion , epilimnion , dissolved organic carbon , mineralization (soil science) , environmental chemistry , organic matter , water column , remineralisation , total organic carbon , nitrogen , chemistry , environmental science , oceanography , nutrient , geology , eutrophication , inorganic chemistry , fluoride , organic chemistry
We tested the hypothesis that dissolved organic matter (DOM) is delivered to deep layers by convective mixing in winter, where it contributes to the mineralization of C, N, and P in the oxygenated hypolimnion of large (surface area 674 km 2 , maximum depth 104 m), monomictic Lake Biwa. Basin‐scale, seasonal measurements of DOM concentrations revealed that dissolved organic carbon (DOC) and nitrogen (DON) accumulated in the epilimnion during warm seasons and were redistributed into the deeper layer during winter overturn. Hypolimnetic DOC and DON decreased in concentration over the stratification period, indicating mineralization; the contributions of DOM to the total mineralization of C and N were 8% and 30%, respectively. Higher contribution of N relative to C suggests that the N‐rich DOM was mineralized at depth. We failed to detect a significant contribution of dissolved organic phosphorus to P mineralization in the hypolimnion, which could be explained by substantial depletion in P relative to C and N of DOM; C: P and N: P ratios were 1,978 and 147, respectively. The data suggest that convective mixing in this monomictic basin delivers DOM to hypolimnetic depths, where it is mineralized during subsequent periods of stratification.