The effects of simulated wastewater nutrient amendments on Sphagnum productivity and decomposition within a subarctic ribbed fen1

Abstract

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, climate regulation, and water polishing. The HBL is a location for current and proposed industrial mining development projects, and its peatlands may become increasingly used to polish treated wastewater from mining camps. This study focuses on biological changes in the Sphagnum moss community associated with the addition of simulated treated domestic wastewater to a subarctic ribbed 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 ribbed fen. Field experiment 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, nutrient content, or decomposition rate 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. A laboratory peat incubation experiment was conducted to determine how increasing exposure to the wastewater nutrients would affect Sphagnum decay potentials. Lab results indicate that greater concentrations of nutrient additions to incubation environments did not significantly increase the amount of CO2 or CH4 emissions. However, origin of the peat and the species of Sphagnum moss comprising the peat was found to be important factors contributing to Sphagnum decomposability and greenhouse gas emissions. Peat formed within a nutrient enriched location produced significantly greater CO2 and CH4 emissions than peat originating from non-fertilized locations, and hollow dominant Sphagnum species show greater decomposability than hummock forming species. makers and industries will consult these results for mining development projects within the HBL and elsewhere in subarctic and boreal biomes.