The algae energy pathway: An emerging mechanism for energy transfer in northern peatlands

Abstract Microbial photoautotrophs (i.e. algae) are increasingly recognized for their importance to the global carbon cycle. This is especially true in carbon‐accumulating ecosystems such as peatlands, where the capacity for carbon storage is substantial but also vulnerable to climate change. The potential for peatlands to store carbon in the future hinges largely on the magnitude of microbially mediated carbon cycling. Warmer temperatures are promoting the release of carbon dioxide (CO 2 ) stored through traditional detrital energy pathways (i.e. peat formation), but climate change is also facilitating the expansion of aquatic habitat across the boreal landscape and increasing nutrient availability, thereby promoting carbon uptake through an algal energy pathway. Algae provide a labile source of energy to both the microbial loop and higher trophic levels, making this new energy pathway susceptible to top‐down regulation. Synthesis . We synthesized research from northern peatlands showing how recent environmental conditions set in place by climate change can govern CO 2 emissions by regulating the composition of microbes on peat surface layers. We highlight conditions such as expanding areas of aquatic habitat and enhanced nutrient cycling that favour algal‐mediated carbon uptake and demonstrate how the presence or absence of an algal energy pathway can determine the direction of peatland carbon flux.