Thesis

The effects of sediments and associated microbial communities in Zostera marina restoration

Restoration of eelgrass (Zostera marina) is underway in a number of regions, yet transplant success remains inconsistent. Eelgrass bed sediments and the microbial communities therein are not well understood, though they may hold the key to improving restoration practices. This research investigated the sediment geochemistry and associated microbial communities of eelgrass in the San Francisco Bay Estuary, aiming to determine the connection between sediment characteristics and eelgrass transplant survival. Using 16S rRNA amplicon sequencing, microbiome analysis showed significant dissimilarities between natural and restored eelgrass beds, though minimal differences between successful and failed restoration sites. Sediment analyses also showed higher levels of organic matter and clay content at restored sites, particularly at those restored sites at which eelgrass has failed to thrive. Overall, I found microbial and biogeochemical evidence for microbial sulfate reduction and the production of sulfide, a phytotoxic metabolite, that was present most acutely at the failed restoration sites. Additionally, a separate mesocosm experiment examined the feasibility of sediment inoculation as a means of preparing a potential restoration site for eelgrass transplanting, though I found no inoculation effects.

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