Microbial community composition in sediments resists perturbation by nutrient enrichment

Abstract

Functional redundancy in bacterial communities is expected to allow microbial assemblages to survive perturbation by allowing continuity in function despite compositional changes in communities. Recent evidence suggests, however, that microbial communities change both composition and function as a result of disturbance. We present evidence for a third response: resistance. We examined microbial community response to perturbation caused by nutrient enrichment in salt marsh sediments using deep pyrosequencing of 16S rRNA and functional gene microarrays targeting the nirS gene. Composition of the microbial community, as demonstrated by both genes, was unaffected by significant variations in external nutrient supply in our sampling locations, despite demonstrable and diverse nutrient-induced changes in many aspects of marsh ecology. The lack of response to external forcing demonstrates a remarkable uncoupling between microbial composition and ecosystem-level biogeochemical processes and suggests that sediment microbial communities are able to resist some forms of perturbation.

Compartmentalized microbial composition, oxygen gradients and nitrogen fixation in the gut ofOdontotaenius disjunctus

“…Importantly, nifH expression was detected in all gut regions and the FG, MG and PHG not only contained transcripts of N 2 -fixing bacteria related to P. propionicigenes but also groups of aerobic N 2 -fixing bacteria. This co-occurrence of aerobic and anaerobic N-fixers is likely related to presence of microaerophilic regions throughout the beetle gut and indicates some degree of functional redundancy in N 2 fixation (Bowen et al, 2011). As discussed earlier, no spirochete-related nifH transcripts were detected; this observation is likely not related to primer bias, as the same nifH primers were used to identify N 2 -fixing spirochetes in termites (Reid and Lloyd-Jones, 2009).…”

Elevated nitrate enriches microbial functional genes for potential bioremediation of complexly contaminated sediments

“…Few studies have examined the response of microbial communities to nitrate inputs. However, distinctly different results about microbial community responses to elevated nitrate were observed, with some reporting significant changes in the microbial community (Carrino-Kyker et al, 2013) and others showing no effect (Bowen et al, 2011;Carrino-Kyker et al, 2012). The complexity of N cycling and methodologies used for these studies could be one of major reasons for this disparity.…”

Ecosystem metabolism in salt marsh tidal creeks and ponds : applying triple oxygen isotopes and other gas tracers to novel environments

“…Also, spatial heterogeneity in production could explain the differences in the mean rates. But given the otherwise similar hydrographic and characteristics and microbial community composition of the tidal creeks (Deegan et al 2007, Bowen et al 2011) and assumptions related to nutrients and benthic chlorophyll above, it is possible that the increased photosynthetic production of oxygen was the result of the nutrient enrichment experiment.…”

“…While marsh platform processes can drive the observations of the TIDE experiment, it is perhaps surprising that NCP in the nutrient amended tidal creek is not clearly altered by the exposure and oxidation of buried organic matter from collapsing creek banks. Results of investigations on the creeks' microbial communities may help explain this discrepancy: Bowen et al (2011) found that microbial community composition resisted change during long-term nutrient amendment (though the active community may be changing; Kearns et al 2016), and in addition to the estimated change in seasonal GPP, bacterial production increased by a similar proportion in the same creek environments and was most likely supported by labile carbon from the benthic microalgae (Bowen et al 2009). Close coupling of carbon fluxes between benthic microalgae and the bacterial community was similarly reported by Spivak and Ossolinski (2016).…”