Peering into the hidden world: photosynthetic microbes as functionally-significant indicators of peatland degradation and restoration

Peatlands are increasingly being recognised for their importance as global carbon stores, in their role managing water, and as sites of biodiversity value. Microbes are key drivers of peatland functioning, but most research has focused on microbes living within the peat column, which are involved in nutrient cycling and carbon dynamics. However, peatlands, especially ombrotrophic bogs, are also home to large numbers and diverse communities of photosynthetic and mixotrophic microorganisms. Whilst the responses of certain key groups have been previously studied, there is little prior research on the photosynthetic microbial community on peatland surfaces as a whole.
Peatlands in the UK face varied anthropogenic disturbances, such as drainage, nutrient pollution and increased fire risk due to anthropogenic climate change. The responses of the photosynthetic microbial community to these disturbances are not well understood. Until their response patterns have been identified, it is difficult to predict what impacts changes in algal functioning from disturbances (including algal carbon and nitrogen fixation) may have on peatlands. Furthermore, if changes in microalgae community are consistent and measurable, they may have potential for usage as bioindicators. This could allow for better monitoring of peatlands for ‘health status’, as well as guiding restoration work. Using light microscopy and molecular methods, this thesis investigates changes in the photosynthetic microbial community with short- and long-term environmental perturbations and successional processes, and looks for evidence of shifts in community and functional changes.
The peatland photosynthetic microbial community appears to be resistant to the three main stressors included in this thesis: fire, nutrient addition and the presence of trees. Instead, microtopography, Sphagnum spp. cover and moisture appear to be the most important drivers in algal community at this scale. This suggests that, where conditions allow their Sphagnum hosts to persist, algae will also be present and maintain their diversity.