Lake Metabolism: Relationships with Dissolved Organic Carbon and Phosphorus

Recent literature has suggested that for many lakes and rivers, the respiratory breakdown of organic matter (R) exceeds production of organic matter by photosynthesis (gross primary production [GPP]) within the water body. This metabolic balance (GPP < R; "heterotrophy") implies that al...

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Bibliographic Details
Published in:Limnology and oceanography 2003-05, Vol.48 (3), p.1112-1119
Main Authors: Hanson, Paul C., Bade, Darren L., Carpenter, Stephen R., Kratz, Timothy K.
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
Carbon dioxide
Chlorophylls
Fresh water ecosystems
Freshwater
Fundamental and applied biological sciences. Psychology
Groundwater
Lakes
Lentic systems
Limnology
Marine
Phosphorus metabolism
Prairies
Sondes
Surface water
Synecology
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Summary:Recent literature has suggested that for many lakes and rivers, the respiratory breakdown of organic matter (R) exceeds production of organic matter by photosynthesis (gross primary production [GPP]) within the water body. This metabolic balance (GPP < R; "heterotrophy") implies that allochthonous organic matter supports a portion of the aquatic ecosystem's respiration. Evidence that many lakes are heterotrophic comes from diverse approaches, and debate remains over the circumstances in which heterotrophy exists. The methods used to estimate GPP and R and the limited extent of lake types studied, especially with respect to dissolved organic carbon (DOC) and total phosphorus (TP) concentrations, are two reasons for differing conclusions. We deployed O2and CO2sondes to measure diel gas dynamics in the surface waters of 25 lakes. From these data, we calculated GPP, R, and net ecosystem production (NEP = GPP - R). Over the broad range in TP and DOC among the lakes, diel CO2and O2changed on a near 1:1 molar ratio. Metabolism estimates from the two gases were comparable, except at high pH. Most lakes in our data set had negative NEP, but GPP and R appeared to be controlled by different factors. TP correlated strongly with GPP, whereas DOC correlated with R. At low DOC concentrations, GPP and R were nearly equal, but, at higher DOC, GPP and R uncoupled and lakes had negative NEP. Strong correlations between lake metabolism and landscape related variables suggest that allochthonous carbon influences lake metabolism.
ISSN:0024-3590
1939-5590
DOI:10.4319/lo.2003.48.3.1112