Abstract
Particulate matter in estuarine systems hosts microbial communities that can impact biogeochemical cycles. While the bacterial community composition on suspended particles has been previously investigated, especially with regards to how salinity may structure these communities, the archaeal fraction of the microbial community has not received the same attention. Here we investigate both the bacterial and archaeal community composition on two sizes of particles along a riverine discharge gradient in the Broadkill River, DE, USA, to determine whether the archaeal community is selected by similar environmental stressors as the bacteria. We measured salinity, nutrients, and diatom abundances, and use particle size as a proxy for oxygen concentrations. We show that salinity is a strong environmental factor that controls both bacterial and archaeal community composition and oxygen is an additional factor, impacting archaea more than bacteria.
Highlights
Particulate matter in aquatic and marine systems harbors diverse microbial communities that contribute to the cycling of nutrients such as carbon, nitrogen, and metals
We show differences in both archaeal and bacterial community structure across the salinity gradient and between particle sizes, suggesting that both salinity and oxygen are forces acting on both microbial domains
Actinobacteria, Betaproteobacteria, and Verrucomicrobia were all present in higher abundances in freshwater across size fractions, while the Alphaproteobacteria, Gammaproteobacteria, Cyanobacteria, and Bacteroidetes were more abundant in higher salinities
Summary
Particulate matter in aquatic and marine systems harbors diverse microbial communities that contribute to the cycling of nutrients such as carbon, nitrogen, and metals. Particle-associated bacterial communities have been studied in habitats around the world, including lakes (Allgaier and Grossart, 2006), rivers and estuaries (Crump et al, 1999; Selje and Simon, 2003; Campbell and Kirchman, 2013), coastal oceans (Bižic-Ionescu et al, 2014), and open oceans (Ganesh et al, 2014). The difference has been attributed to the concentration of nutrients associated with particulate matter, the need for cell-to-cell interactions and attachment, and with the presence of anoxic microhabitats within these particles (Ganesh et al, 2014) These anoxic microhabitats have been well-documented and play a critical role in the assemblage of bacterial communities across studies of particle-associated bacteria. Oxygen gradients within marine snow have been measured with microelectrodes, and completely anoxic regions have been observed in large
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