Impacts of sea-level rise on sediment microbial community structure and function in two New England salt marshes, USA
There is growing evidence for a tight linkage between the structure and function of microbial communities and for the importance of this relationship in ecosystem responses to disturbances such as sea-level rise (SLR). While the role of plants in determining the capacity of salt marshes to keep pace with SLR through sediment accretion has received considerable attention, the role of microbes in offsetting these gains via decomposition is less understood.
Materials and methods
We conducted a controlled experiment to determine the structural and functional responses of microbes to SLR, using soil from the low intertidal zone of two New England salt marshes in Massachusetts and New Hampshire, USA. We used terminal restriction fragment length polymorphisms (t-RFLPs) generated from microbial 16S rDNA to evaluate community composition and diversity and focused on changes in respiration with SLR, measured as total respired carbon normalized by percent organic matter, as a surrogate for decomposition rate.
Results and discussion
We observed a 24% reduction in microbial respiration with a simulated rise in sea level of 40 cm. This functional change was accompanied by a structural shift in microbial community composition among samples from New Hampshire but not Massachusetts, assessed via principal coordinate analysis of t-RFLP data. We also found greater microbial diversity within our New Hampshire samples, suggesting that low diversity may constrain community compositional shifts.
Our results suggest that decreased microbial respiration could alleviate the negative effects of SLR on salt marsh surface elevation, at least in the short term, and that the diversity of the soil microbial community may positively influence functional responses such as respiration.
KeywordsMicrobial community structure Microbial diversity Microbial respiration Sea-level rise Terminal restriction fragment length polymorphisms
We acknowledge Ryan Kingston, Bin Yang, Sultan Ghuman, and Gale Loescher for their help with field collections and microbial cage construction. For granting us access to the marsh sites, we thank Michele Dionne, Paul Stacey, Chris Weidman, Bob Scarborough, Patricia Delgado, and Linda Blum. We thank Shaun Gill and Tim Arienti for their help and expertise with the flow-through seawater system. Funding for this research was provided by the University of New England Biology graduate program. This research (or a portion thereof) was conducted in the National Estuarine Research Reserve System under a Graduate Research Fellowship award to M. Simon from the National Oceanic and Atmospheric Administration.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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