The Earth’s subsurface represents a complex electrochemical environment that contains many electro-active chemical compounds that are relevant for a wide array of biologically driven ecosystem... Show moreThe Earth’s subsurface represents a complex electrochemical environment that contains many electro-active chemical compounds that are relevant for a wide array of biologically driven ecosystem processes. Concentrations of many of these electro-active compounds within Earth’s subsurface environments fluctuate during the day and over seasons. This has been observed for surface waters, sediments and continental soils. This variability can affect particularly small, relatively immobile organisms living in these environments. While various drivers have been identified, a comprehensive understanding of the causes and consequences of spatio-temporal variability in subsurface electrochemistry is still lacking. Here we propose that variations in atmospheric electricity (AE) can influence the electrochemical environments of soils, water bodies and their sediments, with implications that are likely relevant for a wide range of organisms and ecosystem processes. We tested this hypothesis in field and laboratory case studies. Based on measurements of subsurface redox conditions in soils and sediment, we found evidence for both local and global variation in AE with corresponding patterns in subsurface redox conditions. In the laboratory, bacterial respiratory responses, electron transport activity and H2S production were observed to be causally linked to changes in atmospheric cation concentrations. We argue that such patterns are part of an overlooked phenomenon. This recognition widens our conceptual understanding of chemical and biological processes in the Earth’s subsurface and their interactions with the atmosphere and the physical environment. Show less
Hunting, E.R.; Vijver, M.G.; Geest, H.G. van der; Mulder, C.; Kraak, M.H.S.; Breure, A.M.; Admiraal, W. 2015
Decomposition of organic matter is an important ecosystem process governed in part by 33 bacteria. The process of decomposition is expected to benefit from interspecific bacterial 34 interactions... Show moreDecomposition of organic matter is an important ecosystem process governed in part by 33 bacteria. The process of decomposition is expected to benefit from interspecific bacterial 34 interactions such as resource partitioning and facilitation. However, the relative 35 importance of resource niche breadth (metabolic diversity) and resource niche overlap 36 (functional redundancy) on decomposition and the temporal stability of ecosystem 37 processes received little scientific attention. Therefore, this study aims to evaluate the 38 effect of an increase in bacterial community resemblance on both decomposition and the 39 stability of bacterial metabolism in aquatic sediments. To this end, we performed 40 laboratory microcosm experiments in which we examined the influence of bacterial 41 consortia differing in number and composition of species on bacterial activity (Electron 42 Transport System Activity, ETSA), dissolved organic carbon production and wavelet 43 transformed measurements of redox potential (Eh). Single substrate affinities of the 44 individual bacterial species in order to calculate the metabolic diversity of the microbial 45 community. Results presented here indicate that bacterial activity and organic matter 46 decomposition increase with widening of the resource niche breadth, and that metabolic 47 stability increases with increasing overlap in bacterial resource niches, hinting that 48 resource niche overlap can promote the stability of bacterial community metabolism. Show less
