| Summary: | Peatlands dominate the flat landscape of the Hudson Bay Lowland (HBL). Sphagnum mosses are the key peat-generating plants allowing for important ecosystem services such as carbon storage and water polishing. The HBL also has current and proposed industrial mining development projects, and its peatlands may become increasingly used to polish secondarily-treated wastewater from mining camps. We examined biological changes in the plant community associated with the addition of simulated secondarily-treated wastewater to a subarctic ladder fen, a wetland type commonly found throughout the HBL. We determined how the nutrient additions affected the productivity, decomposition, and nutrient ratios within the ponds and raised peatland ridge components of the ladder fen. Our results show between a four to twelvefold increase in productivity rates of the low-lying Sphagnum rubellum species, and a twofold increase in productivity for the higher hummock or ridge-dominating species Sphagnum fuscum in locations closest to the point source of nutrient effluent. Regions of the experimental ribbed fen greater than 50 m away from the point source showed little difference in productivity rates or nutrient content than the reference fen levels. No significant changes to the rate of decomposition of Sphagnum were observed with relation to distance away from point source nutrients as the experimental fen decomposition rates were comparable to the reference fen rates. Sphagnum productivity per year remained greater than mass lost to decomposition. Therefore, this study suggests that, in the short-term, subarctic peatlands exposed to nutrient levels comparable to that present in treated domestic wastewater will increase their capacity to generate Sphagnum-peat and store carbon. This experimental research aids in understanding to what degree plants mediate shifts in ecosystem dynamics within subarctic ladder fens. Policy makers, community planners, and industries may consult these results for mining development projects within the HBL ...
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