Severe droughts are expected to occur with increasing frequency under current climate change models. Droughts conditions lead to changes in the chemistry of salt marsh sediment by raising salinity, decreasing pH, and shifting conditions from anoxic to oxic. These changes have the potential to impact salt marsh microbial communities, including those involved in the nitrogen cycle. Ammonia-oxidizing archaea (AOA) carry out the oxidation of ammonia (NH3) to nitrite (NO2−), the first and most rate limiting step of nitrification. I analyzed community composition and abundance of AOA in sediment samples collected from a Connecticut salt marsh during 2016, a severe drought year, and two non-drought years (2014 and 2017). Samples were collected from sites dominated by short-form Spartina alterniflora (SSA), tall-form Spartina alterniflora (TSA), Spartina patens (SP), and the microbial mat (MAT). Results revealed a significant difference in overall AOA community composition, but not abundance, during the drought year. A significant shift in community composition during the drought year was seen in SSA and TSA sites, but not SP or MAT sites. This change in AOA community composition may signify differences in nitrogen cycling at the marsh.
McMahon, Hayley, "The Effects of Drought on Ammonia-oxidizing Archaea in Salt Marshes" (2018). Biology Honors Papers. 26.
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