TY - JOUR T1 - The effect of carbon subsidies on marine planktonic niche partitioning and recruitment during biofilm assembly JF - bioRxiv DO - 10.1101/013938 SP - 013938 AU - Charles Pepe-Ranney AU - Edward Hall Y1 - 2015/01/01 UR - http://biorxiv.org/content/early/2015/01/16/013938.abstract N2 - The influence of resource availability on planktonic and biofilm microbial community membership is poorly understood. Heterotrophic bacteria derive some to all of their organic carbon (C) from photoautotrophs while simultaneously competing for inorganic nutrients such as phosphorus (P) or nitrogen (N). Therefore, C inputs have the potential to shift the competitive balance of aquatic microbial communities by increasing the resource space available to heterotrophic bacteria (more C) while decreasing the resource space available to algae (less mineral nutrients due to increased competition from osmotrophic heterotrophs). To test how resource dynamics affect membership of planktonic communities and assembly of biofilm communities we amended a series of flow-through mesocosms with C and P to alter the availability of C among treatments. Each mesoscosm was fed with unfiltered seawater and incubated with sterile glass substrate for biofilm formation. We used 454 pyrosequencing of bacterial 16S and 23S plastid genes to ask how resource driven shifts in the pool size of each community affected community membership and structure. The highest C treatment had the lowest planktonic algal abundance yet highest planktonic bacterial abundance and highest biofilm biomass. Resource amendments did not have a significant effect on alpha diversity in either the planktonic or biofilm communities. Rather the biofilm communities consistently had higher alpha diversity than the planktonic communities in all mesocosms. Bacterioplankton and biofilm membership was distinct in all but the highest C treatment where biofilm and planktonic communities increasingly resembled each other over time. Unlike the bacteria, algal biofilm and plankton communities displayed distinct microbial membership and structure in all treatments including the highest C treatment. Our results suggest that even though resource amendments affect community membership, microbial lifestyle (biofilm or planktonic) places a significanlty stronger constraint on community assembly and membership. ER -