Organic matter compositions of rivers draining into Hudson Bay: Present-day trends and potential as recorders of future climate change

Abstract

Concentrations and compositions of particulate and dissolved organic carbon (POC and DOC, respectively) and aromatic compounds including lignin were analyzed in water samples from 17 rivers flowing into Hudson Bay, northern Canada. These rivers incorporate basins to the south with no permafrost to basins in the north with continuous permafrost, and dominant vegetation systems that include Boreal Forest, the Hudson Plains, Taiga Shield, and Tundra. Major latitudinal trends in organic carbon and lignin concentrations and compositions were evident, with both DOC and dissolved lignin concentrations dominating over their particulate counterparts and exhibiting significant correlations with total dissolved and suspended solids, respectively. The composition of lignin reaction products in terms of the syringyl, cinnamyl, and vanillyl compositions indicate mixed sources of vascular land plant‐derived organic carbon, with woody gymnosperms contributions dominating in the southern river basins whereas nonwoody angiosperm sources were more important in the most northerly rivers. The composition of nonlignin aromatic compounds, which provides a tracer for nonvascular plant contributions, suggests stronger contributions from Sphagnum mosses to dissolved organic matter in rivers below the tree line, including those with large peat bogs in their basins. Acid/aldehyde ratios of the lignin products together with Δ14C data for DOC in selected rivers indicate that DOC has generally undergone greater alteration than POC. Interestingly, several northern rivers exhibited relatively old DOC according to the Δ14C data suggesting that either old DOC is being released from permafrost or old DOC survives river transport in these rivers.

Total organic carbon concentrations in ecosystem solutions of a remote tropical montane forest respond to global environmental change

“…This would be in line with Godin et al. (2017), Kalbitz et al. (2000), and Raymond and Hopkinson (2003) who also found that DOM contains mainly young components by 14 C dating.…”

“…The dating of the DOM in the various ecosystem solutions supports our hypothesis that DOM in rainfall originated from fresh plant tissue in the forest canopies and in the mineral soil solutions from canopy leachates, aboveground and belowground litter, or root exudates. This would be in line with Godin et al (2017), , and Raymond and Hopkinson (2003) who also found that DOM contains mainly young components by 14 C dating.…”

Hurricanes Accelerate Dissolved Organic Carbon Cycling in Coastal Ecosystems

“…The compositional lignin phenol parameters S/V, and C/V ranged from 0.32 to 0.48, and 0.06 to 0.13, respectively, and did not exhibit substantial changes with locations and time ( Table 1 and Figure 4). S/V and C/V are generally employed to explore sources of tDOC (i.e., angiosperm versus gymnosperm and woody versus nonwoody) (Hedges and Mann, 1979;Goñi and Hedges, 1995;Godin et al, 2017). Representative tissues and their leachates were integrated in Figure 4 to aid with identification of tDOC sources ( Supplementary Table S1).…”

Seasonal and Geographic Variation in Dissolved Carbon Biogeochemistry of Rivers Draining to the Canadian Arctic Ocean and Hudson Bay

“…As a result, these large systems are unlikely to be representative of the distributed array of smaller watersheds that comprise a significant proportion of the Arctic basin. Measurements characterizing the biogeochemistry of smaller rivers in Alaska (Townsend‐Small et al, ), Siberia (Johnston et al, ), around Hudson Bay (Godin et al, ), and in the Canadian Arctic Archipelago (Alkire et al, ) have provided well‐defined estimates of water chemistry, but over relatively constrained spatial scales, or—because of logistical constraints—based on a relatively small number of samples. In Canada in particular, we know little about the 75% of the Arctic‐flowing drainage that lies outside of the well‐characterized Mackenzie system (see also Alkire et al, and Godin et al, , for recent progress).…”

“…Measurements characterizing the biogeochemistry of smaller rivers in Alaska (Townsend‐Small et al, ), Siberia (Johnston et al, ), around Hudson Bay (Godin et al, ), and in the Canadian Arctic Archipelago (Alkire et al, ) have provided well‐defined estimates of water chemistry, but over relatively constrained spatial scales, or—because of logistical constraints—based on a relatively small number of samples. In Canada in particular, we know little about the 75% of the Arctic‐flowing drainage that lies outside of the well‐characterized Mackenzie system (see also Alkire et al, and Godin et al, , for recent progress). This lack of knowledge exists despite evidence of increasing fluxes of dissolved carbon and ions from several Canadian Arctic locations, which appear to be driven by thawing permafrost and other factors related to climate change (Kokelj et al, ; Spence et al, ; Tank et al, ).…”