Regional Similarities and Consistent Patterns of Local Variation in Beach Sand Bacterial Communities throughout the Northern Hemisphere

Abstract

Recent characterization of the bacterial community structure in beach sands has revealed patterns of biogeography similar to those observed in aquatic environments. Studies to date, however, have mainly focused on subtidal sediments from marine beaches. Here, we investigate the bacterial diversity, using Illumina-based sequencing of the V5-V6 region of the 16S rRNA gene, at 11 beaches representing those next to the Great Lakes, Florida, and the Pacific Ocean. The alpha diversity differed significantly among regions (P < 0.0001), while the within-region diversity was more similar. The beta diversity also differed by region (P < 0.001), where freshwater sands had significantly higher abundances of taxa within the Actinobacteria, Betaproteobacteria, and Verrucomicrobia than marine environments. In contrast, marine sands harbored greater abundances of Gammaproteobacteria and Planctomycetes, and those from Florida had more Deltaproteobacteria and Firmicutes. Marine beaches had significantly different phylogenetic community structures (P < 0.018), but freshwater and Florida beaches showed fewer within-region phylogenetic differences. Furthermore, regionally distinct patterns in taxonomic variation were observed in backshore sands, which had communities distinct from those in nearshore sands (P < 0.001). Sample depth minimally influenced the community composition. The results of this study reveal distinct bacterial community structures in sand on a broad geographic scale but moderate regional similarity and suggest that local variation is primarily related to the distance from the shoreline. This study offers a novel comparison of the bacterial communities in freshwater and marine beach sands and provides an important basis for future comparisons and analyses to elucidate factors affecting microbial ecology in this underexplored environment. IMPORTANCEThis study presents a large-scale geographic characterization of the bacterial communities present in beach sands. While previous studies have evaluated how environmental factors influence bacterial community composition, few have evaluated bacterial communities in freshwater sands. Furthermore, the use of a consistent methodology to characterize bacterial communities here allowed a novel comparison of communities across geographic regions. We reveal that while the community composition in sands at individual beaches is distinct, beach sands within the same region harbor similar assemblages of bacteria and these assemblages differ greatly between regions. In addition, moisture, associated with distance from the shoreline, strongly influences the bacteria present in sands and more strongly influences the bacteria present than sample depth does. Thus, the data presented here offer an important basis for a broader characterization of the ecology of bacteria in sands, which may also be relevant to public health and resource management initiatives.

Environmental Filtering Drives the Assembly of Habitat Generalists and Specialists in the Coastal Sand Microbial Communities of Southern China

“…However, although interactions between site and season significantly influenced the sand microbial assemblages ( Table 1), two of the triplicate samples from the supratidal zone of site JL2 tended to cluster with those from the intertidal zone ( Figure S2). This is might be due to the influence of some large tidal events [7]. Nevertheless, these results are in accordance with the findings of previous studies, where salinity was described as a predominant factor in determining microbial biogeography [43][44][45][46][47].…”

“…Furthermore, the indigenous microbial sand communities are also one of the most critical factors for preventing the colonization of harmful exogenous microorganisms, such as fecal indicator bacteria and pathogens, on beach sands [5,6]. Thus, increasing attention is being paid to the biogeographic distribution pattern of sand microbial communities and its driving forces [2,4,[7][8][9]. The importance of environmental filtering in shaping the assembly of sand microbial communities has highlighted, and a significant body of literature has demonstrated, that the distance from shoreline, sand grain size, moisture, temperature, nutrients (including organic and inorganic matters), and chemical contaminants are major environmental factors shaping sand microbial communities [2,7,8,10,11].…”

“…Thus, increasing attention is being paid to the biogeographic distribution pattern of sand microbial communities and its driving forces [2,4,[7][8][9]. The importance of environmental filtering in shaping the assembly of sand microbial communities has highlighted, and a significant body of literature has demonstrated, that the distance from shoreline, sand grain size, moisture, temperature, nutrients (including organic and inorganic matters), and chemical contaminants are major environmental factors shaping sand microbial communities [2,7,8,10,11]. Therefore, sand microbial assemblages have been proposed as a sensitive bio-indicator for evaluating the environmental health of coastal habitats [10,12].…”

Do composition and diversity of bacterial communities and abiotic conditions of spring water reflect characteristics of groundwater ecosystems exposed to different agricultural activities?

“…Due to the fact that geochemical characteristics are the main drivers of BCC (Constancias et al., ), and since geochemical characteristics differ only slightly across sampling sites, we suggest that this results in a similar taxonomic community composition at the phylum level. This was not unexpected and confirms observations reported by Staley and Sadowsky () that variation in community composition tends to be smaller within the same region. However, differences in taxonomic community composition between sampling sites were more apparent at the family level.…”

“…Due to the fact that geochemical characteristics are the main drivers of BCC (Constancias et al, 2015), and since geochemical characteristics differ only slightly across sampling sites, we suggest that this results in a similar taxonomic community composition at the phylum level. This was not unexpected and confirms observations reported by Staley and Sadowsky (2016) between sampling sites were more apparent at the family level. In conjunction with the results of bacterial diversity, it is most likely that significant differences in diversity estimates across sampling sites are driven by the proportion of rare families, notably for sampling site BB3, where rare families compose approximately 61% of the overall abundance ( Figure 4B).…”