A preliminary organic carbon budget for a small dystrophic lake in Maritime Canada

Abstract

The results of a preliminary organic budget for a small (1.13 h) dystrophic lake in Maritime Canada are presented. Wood's Pond is moderately autotrophically productive (395 mg C m-2 day-'). Allochthonous inputs overwhelmed autochthonous production by an approximate ratio of 9.7:1. Seepage through the surrounding Sphagnum mosses accounted for 89.9% of all organic carbon entering the lake while fluvial transport was responsible for over 90% of losses. The yearly balance was a net loss of approximately 1 820 kg C. The marked dominance of allochthonous inputs over autochthonous production obviously influences the physico-chemical limnology of Wood's Pond but it does not necessarily follow that this system is heterotrophic. The yearly autotrophic production, approximately 1466 kg C, essentially balances an annual community respiration and insect emergence of 1 481 kg C. This suggests that, at least in theory, the biological functioning of this dystrophic lake system could be driven almost entirely by autotrophic production.

Dissolved organic carbon fluctuations in Dal Lake waters

“…Statistically also relationship was observed to exist between pH and DOC on one hand and DOC and temperature on the other (Figs. 3 & 4) with correlation coefficients of -0.649 and -0.59 respectively which is in agreement with the results of Carpenter et al (1983).…”

Variability in organic carbon reactivity across lake residence time and trophic gradients

“…Across the full dataset, mean DOCout/DOCin was 0.70 (standard deviation 0. 31 were highly significant between oligotrophic and eutrophic sites (p < 0.001), and between mesotrophic and eutrophic sites (p = 0.004), but non-significant between oligotrophic and mesotrophic sites (p = 0.23). Regardless of whether sites were net DOC sources or sinks, the overall rate and magnitude of DOC change was strongly influenced by WRT.…”

“…For lakes with multiple sampled inflows [DOC]in was calculated by weighting the mean concentrations of each inflow according to either gauged water discharge for each inflow (if reported) or alternatively according to subcatchment area. Although DOC input to waterbodies can occur through direct precipitation to the water surface, most studies that measured this flux found that it only contributed a few percent of the total DOC input 31,32 . Because few studies reported rainfall fluxed, we assumed a zero DOC input via this pathway in all studies.…”

Carbon source/sink function of a subtropical, eutrophic lake determined from an overall mass balance and a gas exchange and carbon burial balance

“…Net primary production (NPP) was measured monthly at Stations I, II and III using the lightedark bottle method and Winkler oxygen analysis (APHA, 1995). In some studies primary production was considered in the carbon input (Carpenter et al, 1983;Quay et al, 1986). By taking up gaseous CO 2 the phytoplankton has an active role in creating concentration difference between the lake surface and the atmosphere, which is crucial for CO 2 influx.…”

“…Previous carbon budget studies in northern temperate mesotrophic and dystrophic lakes, using an overall mass balance method, where CH 4 was not taken into account, showed that lakes could be a carbon source (Carpenter et al, 1983) or carbon sink (Cole et al, 1989;Eadie and Robertson, 1976). Carbon budget studies using a gas exchange and carbon burial balance showed the ratio of gaseous carbon exchange across the watereair interface of most northern temperate lakes to be greater than 1, similar to the average global ratio for lakes which is also greater than 1 indicating that most lakes are a carbon source (Algesten et al, 2004;Cole and Caraco, 1998;Dillon and Molot, 1997;Hanson et al, 2004) (Table 3).…”