Carbon dioxide dynamics and fluxes in coastal waters influenced by river plumes

Identification of di- and triterpenoid lipid tracers confirms the significant role of autoxidation in the degradation of terrestrial vascular plant material in the Canadian Arctic

“…Several recent studies have confirmed that, under some oceanographic conditions, particulate OM (POM) delivered by rivers may be sensitive to microbial remineralization in the Arctic shelf areas (van Dongen et al, 2008;Karlsson et al, 2010;Vonk et al, 2010). These observations are consistent with the role of estuaries as a source of CO2 for the atmosphere (Raymond et al, 1997(Raymond et al, , 2000Frankignoulle et al, 1998;Cai et al, 2006Cai et al, , 2014. This unexpected microbial lability of terrestrial OM (TerrOM) may be attributed to: (i) the fact that bacterial assemblages in the marine environment can use specific parts of terrestrial POM more effectively than such assemblages in soils and rivers (Garneau et al, 2008), (ii) the involvement of a 'priming effect' (enhanced remineralization of terrestrial OM in the presence of fresh substrates from an algal source; Bianchi, 2011;Ward et al, 2016), or (iii) the formation of free radicals from extracellular non-enzymatic steps, including those generated during wood decomposition by certain Basidiomycotina fungi (i.e.…”

The carbon dioxide system on the Mississippi River‐dominated continental shelf in the northern Gulf of Mexico: 1. Distribution and air‐sea CO2 flux

“…Mechanistic analysis in sections 2.4 and 3.3.3 demonstrates that biological removal and mixing were the two dominant factors influencing p CO 2 along the salinity gradient. As predicted from carbon dynamics during river‐to‐sea mixing, the conservative mixing lines of p CO 2 are concave upward along the salinity gradient [ Cai et al ., ] (Figure ). Along this concave‐upward curve, the p CO 2 difference between salinities 18 and 36 (salinity regions which covered the majority of this study area) was 124, 346, 185, and 117 μatm in spring, summer, fall, and winter, respectively.…”

“…The large freshwater discharge and nitrogen loading contribute to distinct river‐ocean mixing dynamics that are associated with enhanced biological production, both leading to low p CO 2 in the plume and the adjacent coastal system [ Cooley and Yager , ; Salisbury et al ., ; Cai et al ., ; Tseng et al ., ]. Prior studies in this region provide evidence of strong nutrient enhancement of biological production [ Dagg et al ., ; Green et al ., ; Murrell et al ., ; Turner and Rabalais , ] that contribute to strong drawdown of CO 2 in the moderate salinity region coinciding with the location of maximum nutrient removal [ Guo et al ., ; Huang et al ., ].…”

Sea‐air exchange patterns along the central and outer East Siberian Arctic Shelf as inferred from continuous CO2, stable isotope, and bulk chemistry measurements

“…The Global Biogeochemical Cycles 10.1002/2017GB005656 area-weighted median uptake would be 9.4 g C m À2 yr À1 (Table 6). For comparisons, the shelf waters dominated by the plumes of the Amazon, the Mississippi, and the Changijang show similar uptake rates of 6, 12, and 23 g C m À2 yr À1 , respectively [Borges and Abril, 2012;Cai et al, 2014;Körtzinger, 2003]. To conclude, the regional patterns with supersaturation in the inner and shallower parts of the ESAS and undersaturation along the central and outer parts of the shelf follow the general concept of outer shelf sea CO 2 pumping as described for example for the North Sea [Thomas et al, 2004] or for the adjacent Chukchi Sea [Bates, 2006] in the ArcO.…”