The influence of water-table depth and pH on the spatial distribution of diatom species in peatlands of the Boreal Shield and Hudson Plains, Canada

Abstract

Diatoms collected from 113 surface peat samples from the Boreal Shield and HudsonPlains show taxonomic distributions that are associated with macro-vegetation type, pH and position relative to the water table, the main environmental variables measured in this study. The overall goal of our research was to determine the ecological distribution and response of diatoms to microhabitat conditions, and to assess the potential for diatoms to be applied as indicators of long-term environmental change in northern peatlands. Our results indicate that diatom assemblage composition was determined by both the broader peatland type (i.e., bog, rich and poor fens) and microhabitats within peatland formations (e.g., hummock, hollows). The diatom assemblages were primarily influenced by pH with the sites divided at a critical pH of 5.5, and secondarily by the depth of the water table. Acidic bog hollow and hummock microhabitats were species poor and dominated almost exclusively by Eunotia paludosa and/or Eunotia mucophila.These acidophilic and aerophilic diatom species were associated with the narrow pH optima of the dominant Sphagnum species (e.g., S. fuscum, S. angustifolium) found in these bog habitats.Rich and poor fen samples, which were less acidic, supported a more diverse diatom assemblage (>30 species) with greater variability in both diatom and bryophyte pH tolerances. The diatom assemblages recorded in bogs and fens of our study are similar to those found in peatlands around the world, demonstrating that diatom species are very specialized to exist in these often harsh semi-aquatic environments. Diatoms from peatlands have great potential as biomonitors of environmental change in these important ecosystems.

Distribution and diversity of diatom assemblages in surficial sediments of shallow lakes in Wapusk National Park (Manitoba, Canada) region of the Hudson Bay Lowlands

“…All of these taxa have previously been reported from peat surface samples and cores in the southern HBL by Hargan et al. (,b). In particular, high relative abundances of E. mucophila and E. neocompacta sensu lato have been found in fossil diatom assemblages marking the onset of bog conditions in a core collected from a peatland (Hargan et al.…”

“…, ; Hargan et al. ) and has been associated with particular Sphagnum species (e.g., Buczkó ). Hargan et al.…”

“…Hargan et al. (), however, suggested that these close associations may be simply attributable to overlap in pH and moisture preferences.…”

“…In addition, organic-rich peat in their catchments provides specific microhabitats, which are also probably favorable to the growth of Eunotia taxa. Eunotia mucophila, especially, is common in bog hollows in peatlands (e.g., Chen et al 2012Chen et al , 2014Hargan et al 2015a) and has been associated with particular Sphagnum species (e.g., Buczk o 2006). Hargan et al (2015a), however, suggested that these close associations may be simply attributable to overlap in pH and moisture preferences.…”

A 13 000 year multi‐proxy climate record from central Utah (westernUSA), emphasizing conditions leading to large mass movements

“…Hargan et al . ()noted that high diversity is consistent with neutral to basic fens compared to acidic bogs.…”