Abstract
This study examined seasonal differences in microbial community structure in the sediment of three streams in North Carolina’s Neuse River Basin. Microbes that reside in sediment are at the base of the food chain and have a profound influence on the health of freshwater stream environments. Terminal-Restriction Fragment Length Polymorphism (T-RFLP), molecular fingerprint analysis of 16S rRNA genes was used to examine the diversity of bacterial species in stream sediment. Sediment was sampled in both wet and dry seasons from an agricultural (Bear), mixed urban (Crabtree) and forested (Marks) Creek, and the microbiota examined. Gamma, Alpha and Beta proteobacteria were prevalent species of microbial taxa represented among all sites. Actinobacteria was the next most prevalent species observed, with greater occurrence in dry compared to the wet season. Discernable clustering was observed of Marks and Bear Creek samples collected during the wetter period (September–April), which corresponded with a period of higher precipitation and cooler surface water temperatures. Although not statistically significant, microbial community structure appeared different between season (ANOSIM, R = 0.60; p < 0.10). Principal components analysis confirmed this pattern and showed that the bacterial groups were separated by wet and dry seasonal periods. These results suggest seasonal differences among the microbial community structure in sediment of freshwater streams and that these communities may respond to changes in precipitation during wetter periods.
Highlights
Microbial communities in freshwater streams are a diverse functional assemblage of bacteria that include prokaryotes, microeukaryotic phototrophs a nd heterotrophs that influence key processes in stream nutrient cycles [1]
Stream sampling sites were located in the upper Neuse River Basin (NRB), which encompasses a large area (15 km2 ) including metropolitan Raleigh, North Carolina
Taxonomic microbial classification of observed OTU patterns was evaluated for all sites using the non-parametric analysis of similarity (ANOSIM) procedure
Summary
Microbial communities in freshwater streams are a diverse functional assemblage of bacteria that include prokaryotes, microeukaryotic phototrophs a nd heterotrophs that influence key processes in stream nutrient cycles [1]. These microbes are vital to the stream food web and changes in their structure or composition can vary on a temporal scale [2], which can have unintended consequences for stream biotic health. Temporal and spatial differences in bacterioplankton population structure have been observed in response to seasonal fluctuations in flow and related limnological conditions [5,6], stream sediment microbial structure is much less understood. Seasonal changes in rainfall can hydrologically fragment stream flow and bacterioplankton population dispersal, impacting the quality of dissolved organic matter that supports these bacterial populations [7]
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