16S rRNA amplicon study of the bacterial community on 0.45-0.8 micron and >8 micron particles in the Broadkill River in Lewes, DE.. Bacterial Community Patterns on Size-Fractioned Particles in the Broadkill River

Particulate matter in estuarine systems has been shown to host microbial communities that can impact nutrient cycling. Salinity and oxygen have been implicated as environmental stressors that dictate the community composition of particle-associated microbes. More studies, however, have focused on bacterial populations than archaeal. Here we investigate bacterial and archaeal community compositions on size-fractioned suspended particles along a salinity gradient of the Broadkill River in coastal Delaware. We examine the effects of stressors on communities of bacteria and archaea, including the analysis of shifts in diatoms. We found that environmental stressors varied by size of particle and by the domain under investigation. Bacteria associated with smaller particles were influenced by salinity, but bacterial on large particles were potentially responding to geochemistry and direct competition with eukaryotes for habitat space, particularly for photosynthesis. We found that archaea are affected by salinity stress to a lower degree than bacteria, but a greater environmental pressure may be anoxic habitat space on larger particles, which results in a higher species richness, particularly of anaerobic groups of archaea, on these large particles.