Spatial and Temporal Distribution of Particulate Organic Carbon in the Winisk River, Northern Ontario
Abstract
The Winisk River begins in the Precambrian rock of the Canadian Shield in Ontario and traverses the Hudson Bay Lowlands before terminating in Hudson Bay. It drains an area of 67,300 km2that is sparsely populated, with remote communities that depend on natural resources. Accelerated decomposition of organic carbon (OC) in the area due to climate change is supported by higher inputs of particulate and dissolved OC to surface waters (Amon et al, 2012). The Winisk River is a particularly important source of OC to Hudson Bay, shown by high rates of lignin accumulation near the mouth of the river (Kuzyk et al., 2008). Webequie First Nation (WFN) is a small community located on Eastwood Island in Winisk Lake. It is the closest community to the proposed massive development of the "Ring of Fire" chromite and other mineral deposits in the James Bay Lowlands. Mine-related developments can be expected to impact water flows, water chemistry, and carbon cycling in the region. We sampled water and sediment at the major inlets to the lake and at the northern outlet within the territorial boundaries to characterize water chemistry, relate lignin compositional patterns to C and N isotopic signatures, and interpret temporal patterns in advance of development and future climate change. Organic C in the sediments ranged from around 1% to around 30%. Samples were analyzed for lignin compounds using a CuO digestion method coupled to GC-MS to identify lignin-phenol monomers, benzoic acids, and p-hydroxy acid. Ratios of 3,5-dihydroxybenzoic acid, P-hydroxy phenols and cinnamyl phenols to total vanillyl phenols indicate that gymnosperm wood and sphagnum peat dominate the OC pool, although the proportions of gymnosperm- and sphagnum-derived material vary between sites. Stable isotope analysis (δ13C, δ15N) suggests that other inputs of OC may be present that are consistent with OM derived from the erosion of older marine sediments. The results support that the proportion of sphagnum mosses and the total particulate OC will increase as warming continues, in accordance with climate change predictions for the region. Amon RMW et al. 2012. Geochim. Cosmochim. Acta 94, 217. Kurzyk ZZA, Goni MA, Stern GA and Macdonald RW. 2008. Marine Chem. 112, 215.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B13C0596G
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0420 Biomolecular and chemical tracers;
- BIOGEOSCIENCESDE: 0424 Biosignatures and proxies;
- BIOGEOSCIENCES