Document Type

Honors Paper

Advisor

Anne Bernhard

Publication Date

2018

Comments

Use restricted to the Connecticut College campus until May 14, 2020.

Abstract

Salt marsh ecosystems exist along a boundary between fresh and saline waterways, and their function is regulated by a variety of physical and chemical cycles. Microbial communities hold many important roles as mediators in these cycles, and like other aspects of the ecosystem are sensitive to changes in their environment. Climate change is expected to bring many obstacles for salt marshes around the world, one being periods of sustained drought. In this study we investigate the impact that a severe seasonal drought had on the abundance and community composition of microbes involved in nitrogen cycling, specifically ammonia-oxidizing bacteria (AOB). An undisturbed Spartina dominated marsh in Barn Island WMA (Stonington, CT) was sampled across vegetation types, before during and after a period of drought. Community abundance was measured with quantitative PCR, and diversity with DNA fingerprinting (T-RFLP) targeting the ammonia monooxygenase gene (amoA). An effect of drought was observed in both abundance and composition for several vegetation types. AOB abundance and diversity increased in S. patens plots during the drought, while other vegetation types had a temporary reduction in both abundance and diversity during drought. Potential increases in oxygen penetration from soil aeration could explain the AOB bloom seen in S. patens, while in other vegetation types the drought may have selected for more tolerant species. Drought frequency is expected to increase with the continuation of global climate change (GCC), and while these results suggest a tolerance by most vegetation types, with habitat and diversity loss the community remains very susceptible.

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The views expressed in this paper are solely those of the author.