Recovery of smelter-impacted peatlands (Sudbury, Ontario): botanical and microbial community perspectives
Date
2023-08-18
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Abstract
Over one century of mineral smelting activities in the Sudbury Basin denuded the
regional landscape of vegetation near Sudbury, Ontario, previously (early 1960s) the once the
world’s largest point source of SO2 and particulate Ni and Cu emissions. In 1986, fourteen years
after the start of major local pollution controls, Gignac and Beckett reported that poor fen
peatlands neighboring a Sudbury smelter contained flat, black, and barren peat, depicting severe
pollutant stresses. I investigated the plant and microbial communities, and interrelated
geochemical controls, in these severely smelter-damaged poor fens. Over the past 35 years
Sphagnum moss, a keystone peatland genus, has re-established in poor fens as close as 4 km to
smelters, whereas in 1986, Sphagnum was not observed until 12 km. Chemical analysis of the
peat showed that total Ni and Cu concentrations in peat samples were lower than in 1986, and
decreased with increasing distance from the smelter. As peatlands are globally important carbon
sinks, with microbial communities mediating peatland C-cycling, I determined how smelter
activity has altered peat moss and soil microbiomes. I showed that microbial community
structure was controlled by plant species and microtopography in endophytic Sphagnum
communities but was primarily influenced by metal contamination and pH in peat. After healthy
Sphagnum and peat plugs were placed into a contaminated peatland. Sphagnum fuscum (a
hummock species) and Sphagnum fallax (a lawn species) showed signs of successful
establishment (expansion and new growth) after two years, suggesting that more efforts should
be made to restore Sudbury’s peatlands. The transplant peat microbiome shifted towards a
community structure mirroring the microbiome of the host peatland illustrating the central role of
this genus as an ecosystem engineer. I conclude my thesis discussion that because Sudbury
peatlands show signs of slow natural recovery and considering the results from the Sphagnum
transplant study, that pollutant legacies are abating to the point that large-scale active restoration
efforts can now begin.
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Keywords
Peatlands, Smelter activity, Metals, Sphagnum moss,, Microbial ecology