Ph.D., University of California, San Diego (Scripps Institution of Oceanography)

 

Telephone: 617-552-4223

E-mail: mosemans@bc.edu

 

Fields of interest

Wetland and microbial ecology, nitrogen cycling, greenhouse gases and global change, biodiversity.

 

Academic profile

Coastal wetlands are well known to rank among the most productive ecosystems on the planet. As such, they may sequester significant amounts of CO2 in plant biomass or anoxic soils. They are also valued for water purification functions and as nurseries. However, these ecosystems currently face unprecedented modifications in nutrient regimes, hydrology, and species composition due to fertilizer use (from intensive agriculture), land conversion (urbanization, diking, sedimentation), sea level rise, and invasive species. My research addresses how human impacts on coastal ecosystems may not only adversely affect wetland function and structure but also how they may indirectly stimulate the production of greenhouse gases (CH4, CO2, and N2O) that are currently increasing in the atmosphere.

 

My prior work has examined one key function, nitrogen fixation, in coastal salt marshes of Southern California, including Mission Bay and Tijuana Estuary. This is the conversion of N2 gas by bacteria in soils and on plants to ammonia, which can be used by other organisms. I found patterns of nitrogen fixation were dynamic and varied with plant species, suggesting close associations of nitrogen-fixing bacteria (diazotrophs) with Spartina foliosa rhizospheres (roots and surrounding sediments). I also found that nitrogen fixation declines when anthropogenic nutrient loading occurs, and that these declines may be prolonged by compounded disturbances such as heavy inputs of sediment from the surrounding watershed. Some evidence for increased diversity and changes in evenness of diazotroph communities was also found in response to nutrient loading. As these microbes play roles in biogeochemistry, productivity, and food webs, such disturbances may shift the function and structure of coastal ecosystems.

 

I continue to be fascinated by the complex and intimate interactions that occur between wetland plants and nitrogen-transforming microbial communities. I have carried these interests to my new position – near more extensive wetlands – on the opposite coast of the U.S. The current focus of my research addresses the significance of wetlands as sources or sinks of greenhouse gases. These roles must be better constrained in order to manage these ecosystems and ameliorate human impacts on climate. In particular, I study the suite of nitrogen transformations by which microbes generate N2O (nitrous oxide) including denitrification and nitrification in wetlands. Isotopic and molecular approaches must be combined with biogeochemical measurements and manipulative field experiments to reveal the key controls on these processes. Thus, this research holds opportunity for students with a range of backgrounds and interests.

 

Undergraduates have been an integral part of my research from the beginning and I enjoy working with them. I invite any interested students – who are not afraid of mud and are willing to work hard – to contact me regarding research opportunities at: mosemans@bc.edu.

 

 

Representative publications

Moseman, S.M., Johnson, R., Zhang, R., and Qian, P.Y. 2009. Differences in cordgrass structure between a mature and developing marsh reflect distinct N2-fixing communities. Wetlands (in press).

 

Moseman, S.M., Zhang, R., Qian, P.Y., and Levin, L.A. 2008. Diversity and functional responses of nitrogen fixing microbes to three wetland invasions. Invasions Biology DOI:10.1007/s10530-008-9227-0.

 

Moseman, S.M. 2007. Opposite diel patterns of nitrogen fixation associated with salt marsh plant species (Spartina foliosa and Salicornia virginica) in Southern California. Marine Ecology 28(2): 276–287.

 

Moseman, S.M., Levin, L.A., Currin, C.A., and  Forder, C. 2004. Infaunal colonization, succession and nutrition of macrobenthic assemblages in a restored wetland at Tijuana Estuary, California. Estuarine, Coastal and Shelf Science 60: 755–770.

 

 

 

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