Microbes associated with two mangrove forest locations experimentally amended with 15NO3- from South Florida and their contribution to nitrogen cycling
We used the natural heterogeneity of mangrove ecotypes to investigate how within-forest variability affects microbial nitrogen transformations. Samples were collected from the same mangrove forest in both the fringing mangrove area with predominantly Rhizophora mangle (red-fringe) and the basin mangrove area with a mix of Rhizophora mangle, Avicennia germinans, and Laguncularia racemosa (mixed-basin) in February and June. We ran continuous flow incubations using the isotope pairing technique to evaluate the fate of 15NO3- at these two mangrove forest locations. We calculated whether this NO3- was removed via denitrification or recycled via the dissimilatory nitrate reduction to ammonium (DNRA). Following the February incubation, we used 16S rRNA gene sequencing to identify the dominant microbial families within each mangrove forest location. We also conducted a field survey to further characterize the mangrove biomass and soil conditions in both forest locations. We found that despite strong physiochemical and microbial differences between mangrove forest location, both the red-fringe and mixed-basin mangrove forest locations processed nitrogen similarly.