Abstract
The microbial communities of lake sediments play key roles in carbon cycling, linking lakes to their surrounding landscapes and to the global climate system as incubators of terrestrial organic matter and emitters of greenhouse gasses, respectively. Here, we amended lake sediments with three different plant leaf litters: a coniferous forest mix, deciduous forest mix, cattails (Typha latifolia) and then examined the bacterial, fungal and methanogen community profiles and abundances. Polyphenols were found to correlate with changes in the bacterial, methanogen, and fungal communities; most notably dominance of fungi over bacteria as polyphenol levels increased with higher abundance of the white rot fungi Phlebia spp. Additionally, we saw a shift in the dominant orders of fermentative bacteria with increasing polyphenol levels, and differences in the dominant methanogen groups, with high CH4 production being more strongly associated with generalist groups of methanogens found at lower polyphenol levels. Our present study provides insights into and basis for future study on how shifting upland and wetland plant communities may influence anaerobic microbial communities and processes in lake sediments, and may alter the fate of terrestrial carbon entering inland waters.
Highlights
Freshwater ecosystems have an important role in the global carbon (C) cycle because they can offset the terrestrial C sink by an estimated 79% via CO2 and CH4 emissions (Bastviken et al, 2011)
We found that microbial communities varied more among litter types than concentrations and were similar between spiked and un-spiked sediments (Figure 2)
We observed changes in the composition, richness and abundance of bacteria, fungi, and methanogens in our sediments amended with different plant litters
Summary
Freshwater ecosystems have an important role in the global carbon (C) cycle because they can offset the terrestrial C sink by an estimated 79% via CO2 and CH4 emissions (Bastviken et al, 2011). Earth’s ∼304 million lakes are big players in C-cycling, harboring sediment microbial communities responsible for decomposing and mineralizing terrestrially derived C, under the form of organic matter (OM) (Downing et al, 2006). With organic-rich sediments that support obligately anaerobic CH4 production. Anaerobic Microbial Plant Litter Decomposers action disturbance of the sediments (Hofmann et al, 2010), which highlights the importance of small lakes for overall lake CH4 budgeting (Bastviken et al, 2008). With CH4 being ∼25 times more potent a greenhouse gas than CO2 over a 100 yr timeframe, it becomes important to understand how microbial decomposers direct terrestrial C into CH4 (Forster et al, 2007)
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