No abstract

[1] We present here the first comprehensive assessment of the carbon (C) footprint associated with the creation of a boreal hydroelectric reservoir (Eastmain-1 in northern Québec, Canada). This is the result of a large-scale, interdisciplinary study that spanned over a 7-years period (2003)(2004)(2005)(2006)(2007)(2008)(2009)), where we quantified the major C gas (CO 2 and CH 4 ) sources and sinks of the terrestrial and aquatic components of the pre-flood landscape, and also for the reservoir following the impoundment in 2006. The pre-flood landscape was roughly neutral in terms of C, and the balance between pre-and post-flood C sources/sinks indicates that the reservoir was initially (first year post-flood in 2006) a large net source of CO 2 (2270 mg C m À2 d À1) but a much smaller source of CH 4 (0.2 mg C m À2 d À1). While net CO 2 emissions declined steeply in subsequent years (down to 835 mg C m À2 d À1 in 2009), net CH 4 emissions remained constant or increased slightly relative to pre-flood emissions. Our results also suggest that the reservoir will continue to emit carbon gas over the long-term at rates exceeding the carbon footprint of the pre-flood landscape, although the sources of C supporting these emissions have yet to be determined. Extrapolation of these empirical trends over the projected life span (100 years) of the reservoir yields integrated long-term net C emissions per energy generation well below the range of the natural-gas combined-cycle, which is considered the current industry standard.

Abstract. Surface water pCO 2 and pCH 4 measurements were taken in the boreal zone of Québec, Canada, from summer 2006 to summer 2008 in Eastmain 1 reservoir and two nearby lakes. The goal of this follow-up was to evaluate annual greenhouse gas (GHG) emissions, including spring emissions (N.B. gross emissions for reservoir), through flux calculations using the thin boundary layer model. Our measurements underscored the winter CO 2 accumulation due to ice cover and the importance of a reliable estimate of spring diffusive emissions as the ice breaks up. We clearly demonstrated that in our systems, diffusive CH 4 flux (in terms of CO 2 equivalent) were of minor importance in the GHG emissions (without CH 4 accumulation under ice), with diffusive CO 2 flux generally accounting for more than 95% of the annual diffusive flux. We also noted the extent of spring diffusive CO 2 emissions (23% to 52%) in the annual carbon budget.

We provide a baseline account as to the type of mangrove that is typical for Guinea, Africa using field based and remotely sensed data. Specifically, the mangroves of the estuarine islands of Mabala and Yélitono were classified using satellite and airborne optical remote sensing data. Mangroves were mapped according to four classes: tall red (Rhizophora racemosa), medium red (R. racemosa), dwarf red (R. mangle and R. harisonii), and black mangrove (Avicennia germinans). Producer's and user's accuracies for the mapping of mangrove from nonmangrove areas were both 98%. When separating amongst the mangrove classes most of the confusion resulted from the medium red mangrove class. Of the 10,442 ha of mangrove mapped, approximately 30% were classified as riverine, dominated by tall R. racemosa. The remaining mangrove areas were dominated by dwarf mangrove of either Rhizophora or A. germinans. Biophysical parameter data collected from 56 transects varied considerably amongst the classes. For the tallest mangrove class, the mean values of height, DBH, estimated LAI, stem density and basal area recorded were 13 m, 15.1 cm, 4.3, 838 stems/ha, and 25.9 m 2 /ha, respectively. In contrast, for A. germinans, values of 3 m, 4.6 cm, 1.5, 2,877 stems/ha, and 6.0 m 2 /ha were calculated, respectively.

Growing concern over the contribution of freshwater reservoirs to increases in atmospheric greenhouse gas (GHG) concentrations and the relevance of long-term continuous measurements has led Fisheries and Oceans Canada, in conjunction with Manitoba Hydro, to develop continuous GHG monitors. Continuous water pCO(2), pCH(4), and pO(2) measurements were gathered to estimate gas fluxes in one temperate reservoir (Riviere-des-Prairies) and two boreal reservoirs (Eastmain-1 and Robert-Bourassa) in Quebec, and in four boreal reservoirs (Grand Rapids, Jenpeg, Kettle, and McArthur Falls) in Manitoba, Canada. Mean daily CO(2) fluxes ranged between 7 and 14 mmolCO(2)*m(-2)*d(-1) in Manitoba and between 15 and 55 mmolCO(2)*m(-2)*d(-1) in Quebec. Summertime episodes of water undersaturation in CO(2) were observed at Jenpeg, Kettle, and McArthur, suggesting higher productivities of these systems compared to the other systems studied. Mean daily CH(4) fluxes ranged between 0 and 69 micromolCH(4)*m(-2)*d(-1) in Manitoba and between 9 and 48 micromolCH(4)*m(-2)*d(-1) in Quebec. Comparisons of results obtained in the Eastmain-1 area using automated monitors, floating chambers or dissolved gas analyses over multiple-station field campaigns demonstrated that a continuous GHG monitor at a single sampling station provided representative and robust results.