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Contributed by Andrea Rinaldo, July 1, 2014 (sent for review March 10, 2014)
Significance
Microbial communities orchestrate most biogeochemical processes on Earth. In streams and rivers, surface-attached and matrix-enclosed biofilms dominate microbial life. Despite the relevance of these biofilms for ecosystem processes (e.g., metabolism and nutrient cycling), it remains unclear how features inherent to stream and river networks affect the fundamental organization of biofilm communities in these ecosystems. We combined co-occurrence analyses of biofilms based on next-generation sequencing with a probabilistic hydrological model, and showed how fragementation of microbial co-occurrence networks change across stream networks. Our analyses offer potential insights into the response of microbial community organization and persistence to human pressures that increasingly change the hydrological regime and biodiversity dynamics in fluvial networks.
Abstract
Recent studies highlight linkages among the architecture of ecological networks, their persistence facing environmental disturbance, and the related patterns of biodiversity. A hitherto unresolved question is whether the structure of the landscape inhabited by organisms leaves an imprint on their ecological networks. We analyzed, based on pyrosequencing profiling of the biofilm communities in 114 streams, how features inherent to fluvial networks affect the co-occurrence networks that the microorganisms form in these biofilms. Our findings suggest that hydrology and metacommunity dynamics, both changing predictably across fluvial networks, affect the fragmentation of the microbial co-occurrence networks throughout the fluvial network. The loss of taxa from co-occurrence networks demonstrates that the removal of gatekeepers disproportionately contributed to network fragmentation, which has potential implications for the functions biofilms fulfill in stream ecosystems. Our findings are critical because of increased anthropogenic pressures deteriorating stream ecosystem integrity and biodiversity.
Footnotes
- ↵1To whom correspondence may be addressed. Email: andrea.rinaldo{at}epfl.ch or tom.battin{at}univie.ac.at.
Author contributions: S.W., K.B., A.R., and T.J.B. designed research; S.W., K.B., G.A.S., S.C., E.B., C.Q., W.T.S., A.R., and T.J.B. performed research; S.W., G.A.S., S.C., E.B., and T.J.B. contributed new reagents/analytic tools; S.W., K.B., G.A.S., S.C., E.B., C.Q., W.T.S., and T.J.B. analyzed data; and S.W., A.R., and T.J.B. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1411723111/-/DCSupplemental.
Freely available online through the PNAS open access option.
Microbial co-occurrence in streams
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