Mangrove bacterial richness.

Mangroves are complex and dynamic ecosystems varying in salinity, water level and nutrient availability; they also contain diverse and distinct microbial communities. Studies of microbes and their interactions with other ecosystem components (e.g., tree roots) are critical for our understanding of mangrove ecosystem functioning and remediation. Using a barcoding pyrosequencing approach, we previously noted the persistence of terrestrial bacterial populations on mangrove roots when nursery raised saplings were transplanted back to their natural environment. Here we go into further detail about the potential functional associations of bacterial guilds with distinct mangrove microhabitats including the rhizosphere. We also use a nonparametric richness estimator to show that estimated operational taxonomic unit (OTU) richness is more than twice that observed. In the transplant microhabitat, our estimate suggests that there are almost 7,000 OTU's for a sample size of 10,400 individual sequences with no sign of an asymptote, indicating that "true" richness for this microhabitat is substantially larger. Results on the number of bacterial OTU's should, however, be viewed with caution given that the barcoding pyrosequencing technique used can yield sequencing artifacts that may inflate richness estimates if not properly removed.