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Ecosystem respiration: drivers of daily variability and background respiration in lakes around the globe

We assembled data from a global network of automated lake observatories to test hypotheses regarding the
drivers of ecosystem metabolism. We estimated daily rates of respiration and gross primary production (GPP) for
up to a full year in each lake, via maximum likelihood fits of a free-water metabolism model to continuous highfrequency
measurements of dissolved oxygen concentrations. Uncertainties were determined by a bootstrap
analysis, allowing lake-days with poorly constrained rate estimates to be down-weighted in subsequent analyses.
GPP and respiration varied considerably among lakes and at seasonal and daily timescales. Mean annual GPP
and respiration ranged from 0.1 to 5.0 mg O2 L-1 d-1 and were positively related to total phosphorus but not
dissolved organic carbon concentration. Within lakes, significant day-to-day differences in respiration were
common despite large uncertainties in estimated rates on some lake-days. Daily variation in GPP explained 5% to
85% of the daily variation in respiration after temperature correction. Respiration was tightly coupled to GPP at a
daily scale in oligotrophic and dystrophic lakes, and more weakly coupled in mesotrophic and eutrophic lakes.
Background respiration ranged from 0.017 to 2.1 mg O2 L-1 d-1 and was positively related to indicators of
recalcitrant allochthonous and autochthonous organic matter loads, but was not clearly related to an indicator of
the quality of allochthonous organic matter inputs.

Timeline: 
2012-09-27

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