ArticlePDF Available

Differential Decay of Wastewater Bacteria and Change of Microbial Communities in Beach Sand and Seawater Microcosms

Authors:

Abstract and Figures

Laboratory microcosm experiments were conducted to determine the decay kinetics of wastewater bacteria and the change of microbial communities in beach sand and seawater. Cultivation-based methods showed that common FIBs (Escherichia coli, enterococci, and Clostridium perfringens) exhibited biphasic decay patterns in all microcosms. Enterococci and C. perfringens, but not E. coli, showed significantly smaller decay rates in beach sand than in seawater. Cultivation-independent qPCR quantification of 16S rRNA gene also showed significantly slower decrease of total bacterial densities in beach sand than in seawater. Microbial community analysis by next-generation sequencing (NGS) further illustrated that the decreasing relative abundance of wastewater bacteria was contrasted by the increase in indigenous beach sand and seawater microbiota, and the overall microbial community dynamics corresponded well with the decay of individual FIB populations. In summary, the differential decay of wastewater bacteria in beach sand and in seawater provides a kinetic explanation to the often-observed higher abundance of FIBs in beach sand, and the NGS-based microbial community analysis can provide valuable insights to understanding the fate of wastewater bacteria in the context of indigenous microbial communities in natural environments.
Content may be subject to copyright.
A preview of the PDF is not available
... Culturable enterococci decayed rapidly in water for up to 2.5 days, before a slower decay phase. The identified slightly higher decay rate of culturable enterococci in this study than noted in earlier studies with coastal waters (4,35,36) The detected biphasic decay of Enterococcus spp. molecular markers (rDNA, rRNA) in water confirmed the recent findings by Ahmed et al. (37). ...
... rRNA). This better persistency detected herein has been reported also in several earlier studies in which the availability of nutrients, protection from UV radiation and predation, and lowered temperature have been identified as factors enhancing the survival (4,5,17,35,36,40,47). Further, the higher persistency of surface attached microbes in sediment or vegetation than in water may be due to the surface biofilm protecting microbes from external stress factors (48). ...
... This finding is in contrast to other studies reporting that the concentrations of fecal indicators (E. coli and Enterococci) are higher in sand (both dry and wet) compared with the adjacent seawater (Beversdorf et al., 2007;Hartz et al., 2008). Bacteria have a higher growth potential in sand because of the ease with which bacteria can adsorb to sand particles and organic matter; sand sediments also provide protection from solar radiation (Pereira et al., 2013;Zhang et al., 2015). ...
Article
Full-text available
Coastal habitats provide important ecosystem services, such as the maintenance of ecological sustainability, water quality regulation, nutrient recycling, and sandy beaches which are important areas for recreation and tourism. The quality of seawater is generally measured by determining the concentrations of Escherichia coli and intestinal Enterococci, which might be affected by the persistent populations of these bacteria in sand. Sand might thus be a significant source of pathogen exposure to beachgoers. The quality of coastal recreational waters can also be affected by eutrophication, water discoloration, and harmful algal blooms, which pose additional human health risks. Here, we conducted a monitoring of the beaches quality along the Taranto Gulf by determining the concentrations of fecal indicator organisms, as well as other parameters that are not traditionally measured (physicochemical parameters, Pseudomonas aeruginosa, and harmful microalgae), in shallow seawater and sand sampled from three beaches. The concentrations of bacteria were determined using both standard microbiological methods and the IDEXX system. Our results demonstrate the utility of measuring a greater number of parameters in addition to those conventionally measured, as well as the importance of assessing the health risks posed by the sand matrix. Additional work is needed to develop rapid analytical techniques that could be used to monitor the microbiological parameters of solid matrices.
... Monitoring terhadap kualitas biologis seringkali dikesampingkan pada kegiatan monitoring kualitas wisata pantai. Sampai saat ini monitoring kualitas biologis pasir pantai kurang diperhatikan dibandingkan kualitas air laut (Wade et al., 2010;Zhang et al., 2015). Keberadaan kelompok coliform khususnya bakteri E. coli dapat menjadi bakteri patogen untuk beberapa kasus penyakit. ...
Article
Full-text available
Marina and Baruna Beach are widely recognized as popular beach tourism destinations in Semarang. Its proximity to the main beach estuary causes them to significantly impact marine tourism quality. In addition, their exposure to waste may be a potential threat to biological pollution. Coliform and Escherichia coli are used as bioindicators to monitor the quality of marine tourism due to their high correlation to faecal contamination and pathogenic microbes. Samples collected were beach sand and seawater from Marina Beach, Baruna Beach and the estuary of Semarang Banjir Kanal Barat. Data were collected following the presumptive and confirmed test, followed by the conversion to MPN Table. Data obtained is combined with Government Regulations No. 22 of 2021 in Appendix VIII, specifically seawater quality standards for marine tourism. The results of this study reveal high contamination of coliform and E. coli in both beaches. Coliform result in the swimming zone at Marina Beach was 2800 MPN/100ml and at Baruna Beach was 16000 MPN/100ml. Meanwhile, Escherichia coli in the swimming zone area at Marina Beach was 400 MPN/100ml and at Baruna Beach was 1700 MPN/100ml. Overall, these results show that the contamination rate from both swimming zones is higher than the recommended seawater quality standard for marine tourism Wisata Pantai Marina dan Pantai Baruna menjadi kawasan wisata pantai yang populer di Kota Semarang. Lokasinya yang berdekatan dengan muara sungai utama di Kota ini berdampak terhadap kualitas wisata pantai. Paparan limbah berpotensi menyebabkanpencemaran biologis. Monitoring terhadap bakteri coliform dan bakteri Escherichia coli dapat digunakan sebagai bioindikator kualitas wisata pantai, karena keberadaannya berkorelasi dengan cemaran feses dan mikroba patogen. Sampel berupa pasir pantai dan air laut diambil dari lokasi Pantai Marina, Pantai Baruna, dan muara Sungai Banjir Kanal Barat Kota Semarang. Pengujian sampel dilaksanakan dengan presumtif test dan confirmed test, selanjutnya dikonversi dengan Tabel MPN. Data yang didapatkan akan dipadukan dengan PP Nomor 22 Tahun 2021 pada Lampiran VIII, yaitu baku mutu air laut untuk wisata bahari. Hasil penelitian menunjukkan tingginya kontaminasi bakteri coliform dan bakteri Escherichia coli dikedua pantai. Hasil coliform pada kawasan swimming zone pada Pantai Marina 2800 MPN/100ml dan Pantai Baruna 16000 MPN/100ml, serta hasil Escherichia coli pada kawasan swimming zone pada Pantai Marina 400 MPN/100ml dan Pantai Baruna 1700 MPN/100ml. Kawasan swimming zone pada wisata Pantai Marina dan Pantai Baruna mempunyai hasil yang melebihi baku mutu air laut untuk wisata bahari.
... Similarly, the initial rate of decay in the dark was approximately 1.1 Â 10 5 CFU/mL/ month while the rate of decay in the second phase was about 5 times lower. Previous studies have also shown biphasic decay of microorganisms (13,14), which is attributed largely to the population heterogeneity and the ability of some bacterial cells to persist in starvation conditions at low cell densities (14,15). Besides, the presence of algae and cyanobacteria may have contributed to the higher HPC in the light compared to that in the dark as heterotrophic microorganisms may depend on the metabolites produced by the primary producers for growth and maintenance (16). ...
Article
Full-text available
Microbial communities play an essential role in maintaining a healthy aquatic ecosystem. For example, in surface water reservoirs, microorganisms produce oxygen, break down toxic contaminants, and remove excess nitrogen.
... Many methodological variations are evident in the literature, including the length and method of shaking, settling time, and composition of elutant (Beversdorf et al., 2007;Boehm et al., 2009;Elmir et al., 2007). Methods for extracting micro-organisms and their nucleic acids from sand are also varied, that is, a membrane filter on which micro-organisms have been concentrated may be transferred directly to DNA extraction (Zhang et al., 2015) while others use the eluate from the slurry method for DNA extraction Zhang et al., 2016). ...
Article
Aims: Beach water quality is regulated by fecal indicator bacteria (FIB) levels, sand is not, despite known human health risk from exposure to beach sand. We compared the performance of three methods to extract bacterial DNA from beach sand as a step toward a standard method. Methods and results: The analytical sensitivity of qPCR for Enterococcus was compared for the slurry (suspension, agitation, membrane filtration of supernatant), vs direct extraction using PowerSoil™ or PowerMax Soil™ kits. The slurry method had the lowest limit of detection at 20-80 GC g-1, recovered significantly more DNA, and the only method that detected Enterococcus by qPCR in all samples; therefore, the only method used in subsequent experiments. The slurry method reflected the spatial variability of Enterococcus in individual transect samples. Mean recovery efficiency of the microbial source tracking marker HF183 from wastewater spiked marine and freshwater beach sand was 100.8% and 64.1%, respectively, but varied, indicating that the mixing protocol needs improvement. Conclusions: Among the three methods, the slurry method had the best analytical sensitivity and produced extracts that were useful for culture or molecular analysis. Significance and impact of study: Standardization of methods for extraction of bacterial DNA from sand facilitates comparisons among studies, and ultimately contributes to the safety of recreational beaches.
... In contrast, PCR marker-based methods target a specific sequence associated with a particular source. Previous efforts have evaluated the persistence of both human markers (Bae and Wuertz, 2009;Ahmed et al., 2014;Mattioli et al., 2017) and wastewater associated bacterial communities in marine waters (Sassoubre et al., 2015;Zhang et al., 2015;Ahmed et al., 2018). Side-by-side comparisons are also needed that evaluate decay of these signals under relevant environmental conditions and to ensure the stability of bacterial community-based pollution assignments. ...
Article
Full-text available
Ocean currents, multiple fecal bacteria input sources, and jurisdictional boundaries can complicate pollution source tracking and associated mitigation and management efforts within the nearshore coastal environment. In this study, multiple microbial source tracking tools were employed to characterize the impact and reach of an ocean wastewater treatment facility discharge in Mexico northward along the coast and across the Southwest United States- Mexico Border. Water samples were evaluated for fecal indicator bacteria (FIB), Enterococcus by culture-based methods, and human-associated genetic marker (HF183) and Enterococcus by droplet digital polymerase chain reaction (ddPCR). In addition, 16S rRNA gene sequence analysis was performed and the SourceTracker algorithm was used to characterize the bacterial community of the wastewater treatment plume and its contribution to beach waters. Sampling dates were chosen based on ocean conditions associated with northern currents. Evidence of a gradient in human fecal pollution that extended north from the wastewater discharge across the United States/Mexico border from the point source was observed using human-associated genetic markers and microbial community analysis. The spatial extent of fecal contamination observed was largely dependent on swell and ocean conditions. These findings demonstrate the utility of a combination of molecular tools for understanding and tracking specific pollutant sources in dynamic coastal water environments.
... Sand pollution is recognised as a significant risk to public health [3][4][5][6][7][8][9][10] . Faecal bacteria can accumulate and survive for long periods of time in sand and their concentrations can be 10 to 100 times greater than those in beach water [11][12][13][14][15] . In addition, after a typhoon event, heterotrophic bacteria, coliform bacteria, Escherichia coli, and enterococci can be 10-10 3 times higher than what is normally detected in beach sand outside the water line 15 . ...
Article
Full-text available
On recreational sandy beaches, there are guidelines for the management of bacterial pollution in coastal waters regarding untreated sewage, urban wastewater, and industrial wastewater. However, terrestrial plant debris on coastal beaches can be abundant especially after floods and whilst it has rarely been considered a concern, the bacterial population associated with this type of pollution from the viewpoint of public health has not been adequately assessed. In this study, microbes associated with plant debris drifting onto Kizaki Beach in Japan were monitored for 8 months throughout the rainy season, summer, typhoon season, and winter. Here we show that faecal-indicator bacteria in the plant debris and sand under the debris were significantly higher than the number of faecal bacteria in the sand after a 2015 typhoon. When we focused on specific pathogenic bacteria, Brevundimonas vesicularis and Pseudomonas alcaligenes were commonly detected only in the plant debris and sand under the debris during the survey period. The prompt removal of plant debris would therefore help create safer beaches.
... Under extreme radiation incidence, sterilization of the water (complete elimination of culturable cells) should not avoid growth in the dark phase. Bacterial decays in the environment usually show an inflection indicating biphasic die-off, as observed by Zhang et al. [41], and, from this work, shown in Fig. 2, after 2 h and 4 h of exposure. In the first 2 h, the average decay rate was strongly influenced by k from assay E (− 2.612 h −1 ), and less from assay G (− 0.112 h −1 ), but in the second inflection, these contributions were reversed (− 0.057 h −1 and − 3.157 h −1 , respectively). ...
Article
Full-text available
In both Brazilian and European regulations, the impact assessment of sewage discharges into coastal waters is based on microbiological analyses of fecal indicators such as Escherichia coli, frequently used in prevision hydrodynamic models. However, the decay rates of E. coli vary depending on environmental conditions, and analysis may lead to inaccurate conclusions. This study aimed to analyze the decay of culturable and viable (but not culturable) E. coli in outdoor conditions, by creating microcosms inoculated with pre-treated sewage. The microcosms were filled with 9.88 L of filtered water (0.22 μm membrane), 3.5% salt, 0.1–0.2% BHI, and 1% bacterial suspension obtained by reverse filtration. PMA-qPCR of E. coli uidA gene and Colilert measurements were applied to evaluate population counts after 2 h, 4 h, and 26 h. After nine hours of exposure to solar radiation, the viable cells decreased to 2.76% (interpolated value) of the initial population, and the cultivable fraction of the viable population accounted for 0.50%. In the dark period, the bacteria grew again, and viable cells reached 8.54%, while cultivable cells grew to 48.14% of initial population. This behavior is possibly due to the use of nutrients recycled from dead cells. Likewise, populations of E. coli in sewage outfalls remain viable in the sediments, where resuspension can renew blooming. Graphic Abstract
Article
Biphasic decay has been observed for indicators and pathogens in bench-scale and in-situ water experiments for decades, however, first-order decay kinetics continue to be applied to persistence data because of their simplicity and ease of application. Model uncertainty introduced by broadly applying first-order decay kinetics to persistence data may lead to erroneous decision making in the fields of water management and protection. As surface waters are exposed to highly variable environmental and water quality factors that influence microbial and viral persistence, it is expected that first-order decay kinetics are not representative of most of the persistence literature for indicators and pathogens in surface water matrices. This review compiled the methods and results of 61 studies that conducted experiments evaluating the persistence of fecal indicator bacteria, bacteriophages, pathogenic bacteria, viruses, and protozoa in natural surface water matrices. The goals of this review were trifold: 1) collate studies in the literature with data available for future persistence modeling, 2) present the current state of knowledge with regards to the environmental and water quality factors affecting persistence in natural surface waters, and 3) identify recurrent evidence for interactions between the frequently studied factors to inform future factor analyses. Comparing the methods and results across the 61 studies suggest potential interactions between sunlight and water type; sunlight and method of detection; predation and water type; predation and temperature; and water type and method of detection. The majority of the identified literature evaluated FIB or bacteria persistence; future experiments are needed that focus on protozoa, brackish or marine water types, and molecular-based methods of detection.
Article
Nitrogen, a critically important nutrient that boosts yields in agriculture and food production, is currently overused to meet the rising demand for food. Surplus nitrogen ends up in the environment in excess of the capacity of natural nitrogen cycle, thereby leading to serious environmental pollutions, such as eutrophication of water bodies and emission of nitrous oxide (a highly potent greenhouse gas) to atmosphere. Aquaponics–bioponics is an emerging soilless technology for nitrogen recovery that links organic vegetable production to aquaculture effluent remediation (aquaponics) or organic waste recycling (bioponics). This Review presents the concept of aquaponics–bioponics for nitrogen recovery. Nitrogen transformations and nitrogen mass distributions in aquaponic–bioponic systems are critically discussed, along with the nutrient availability of several organic composts that can be integrated with the systems, and the microbial communities involved. This discussion is followed by a dynamic nitrogen modeling for managing nitrogen from different wastes in aquaponics–bioponics. Various emerging engineering technologies that could improve aquaponics–bioponics are presented, including aeration with microbubbles and/or nanobubbles, cocultivation with algae, process automation with Internet of Things, and integration with indoor vertical farming (plant factory with artificial light). Overall, the Review lays out the state-of-art in aquaponics–bioponics and highlights potential approaches for developing highly efficient nitrogen recovery technologies from diverse organic waste streams.
Article
Full-text available
Massively parallel sequencing of 16S rRNA genes enables the comparison of terrestrial, aquatic, and host-associated microbial communities with sufficient sequencing depth for robust assessments of both alpha and beta diversity. Establishing standardized protocols for the analysis of microbial communities is dependent on increasing the reproducibility of PCR-based molecular surveys by minimizing sources of methodological bias. In this study, we tested the effects of template concentration, pooling of PCR amplicons, and sample preparation/inter-lane sequencing on the reproducibility associated with paired-end Illumina sequencing of bacterial 16S rRNA genes. Using DNA extracts from soils and fecal samples as templates, we sequenced pooled amplicons and individual reactions for both high (5-10 ng) and low (0.1 ng) template concentrations. In addition, all experimental manipulations were repeated on two separate days and sequenced on two different MiSeq lanes. Although within-sample sequence profiles were highly consistent, template concentration had a significant impact on sample profile variability. Pooling of multiple PCR amplicons influenced the separation of all profiles from each sample and reduced within-sample heterogeneity, although these effects were not always significant. By comparison, sample preparation and inter-lane variability did not influence sample sequence data significantly. This systematic analysis underlines the importance of optimizing template concentration in order to minimize variability in microbial community surveys and indicates that the practice of pooling multiple PCR amplicons prior to sequencing contributes proportionally less to reducing bias in 16S rRNA gene surveys with next-generation sequencing.
Article
Full-text available
Beach sands impact water quality and pathogen loads, however, the comparative decay of the fecal indicator bacteria (FIB) Enterococcus spp. and Escherichia coli, and pathogens in freshwater sand have not been examined. In this study, freshwater sand microcosms were inoculated with sewage and pure cultures of bacterial pathogens to compare relative decay rates. The abundance of culturable Enterococcus spp. and E. coli, genetic markers for Enterococcus spp. (Entero1), total Bacteroides (AllBac), and human-specific Bacteroides (HF183), and genetic markers for the pathogens Campylobacter jejuni, methicillin-resistant Staphylococcus aureus (MRSA), Salmonella enterica subsp. enterica serovar Typhimurium, and Shigella flexneri were monitored over the course of two weeks using conventional culture methods and quantitative PCR (qPCR). The effect of moisture on the persistence of culturable FIB and all genetic markers was also determined. In addition, propidium monoazide (PMA) treatment was used to examine differences in the persistence of total genetic markers and those from live cells. Decay rates were statistically compared using Tukey's test. Moisture had a significant (p ≤ 0.05) effect on the decay rates of culturable indicator bacteria, total AllBac markers, and genetic markers for FIB, Salmonella, and MRSA from live cells. At 14% sand moisture, the decay rate of total markers was slower than that of live cells for all qPCR assays, but at 28% moisture, there was no difference in the decay rates of total and live markers for any assay. AllBac and MRSA markers increased in sand at 28% moisture, probably indicating cellular growth. Overall, culturable FIB and HF183 had decay rates that were most comparable to the bacterial pathogen markers examined in this study, whereas Entero1 and AllBac rarely exhibited decay rates similar to the bacterial pathogens in this study. The choice of FIB for assessment of fecal contamination in freshwater sand should take into account the pathogen of concern and sand moisture conditions.
Article
Full-text available
Recreational water quality, as measured by culturable fecal indicator bacteria (FIB), may be influenced by persistent populations of these bacteria in local sands or wrack, in addition to varied fecal inputs from human and/or animal sources. In this study, pyrosequencing was used to generate short sequence tags of the 16S hypervariable region ribosomal DNA from shallow water samples and from sand samples collected at the high tide line and at the intertidal water line at sites with and without FIB exceedance events. These data were used to examine the sand and water bacterial communities to assess the similarity between samples, and to determine the impact of water quality exceedance events on the community composition. Sequences belonging to a group of bacteria previously identified as alternative fecal indicators were also analyzed in relationship to water quality violation events. We found that sand and water samples hosted distinctly different overall bacterial communities, and there was greater similarity in the community composition between coastal water samples from two distant sites. The dissimilarity between high tide and intertidal sand bacterial communities, although more similar to each other than to water, corresponded to greater tidal range between the samples. Within the group of alternative fecal indicators greater similarity was observed within sand and water from the same site, likely reflecting the anthropogenic contribution at each beach. This study supports the growing evidence that community-based molecular tools can be leveraged to identify the sources and potential impact of fecal pollution in the environment, and furthermore suggests that a more diverse bacterial community in beach sand and water may reflect a less contaminated site and better water quality.
Article
Survival of Escherichia coli MC-6 of fecal origin in an estuarine environment as affected by time, water temperature, dissolved oxygen, salinity, and montmorillonite in diffusion chambers has been elucidated. Several in situ physical parameters were recorded simultaneously, and viable cell numbers were estimated. The survival of the bacteria varied seasonally. Montmorillonite addition extended the time needed for a 50% reduction of the viable cell population (t½) of cells by 40% over the t½ of cells in Rhode River water alone. The effect of this clay was not significantly greater between 50- to 1,000-μg/ml montmorillonite concentrations. In all experiments, the relationships among pairs of variables were studied by regression and correlation analysis. The slope between viable cell numbers and water temperatures increased about 50% for each 10 C increment in temperature and gave a correlation coefficient r = 0.617, significant at 95% confidence level. A similar correlation coefficient, r = 0.670, was obtained between water temperature and t½ of the initial cell population. In all experiments regressions were performed considering all variables after bacteria had been in the Rhode River environment for 3 days. Coefficient of multiple determinaton was estimated as R² = 0.756. Approximately 75.6% of the variance of viable cell numbers can be explained by variation in water temperature, dissolved oxygen, and salinity. Simple correlation coefficients within the regression steps were also computed. Survival of bacteria was closely and negatively correlated with increasing water temperature (r = -0.717). It is suggested that water temperature is the most important factor in predicting fecal coliform survival from point and nonpoint sources in assessing water quality in an estuarine ecosystem.
Article
Billions of gallons of untreated wastewater enter the coastal ocean each year. Once in the marine environment, sewage microorganisms are exposed to environmental stressors such as sunlight and predation. Previous research has investigated the fate of individual sewage microorganisms in seawater but not the entire sewage microbial community. The present study uses next generation sequencing (NGS) to examine how the microbial community in sewage-impacted seawater changes over 48 hours when exposed to natural sunlight cycles and marine microbiota. We compared results from microcosms composed of unfiltered seawater (containing naturally occurring marine microbiota) and filtered seawater (containing no marine microbiota) to investigate the effect of marine microbiota. We also compared results from microcosms that were exposed to natural sunlight cycles with microcosms kept in the dark to investigate the effect of sunlight. The microbial community composition and the relative abundance of operational taxonomic units (OTUs) changed over 48 h in all microcosms. Exposure to sunlight had a significant effect on both community composition and OTU abundance. The effect of marine microbiota, however, was minimal. The proportion of sewage-derived microorganisms present in the microcosms decreased rapidly within 48 h and was most pronounced in the presence of both sunlight and marine microbiota where the proportion decreased from 85% to 3% of the total microbial community. The results from this study demonstrate the strong effect sunlight has on microbial community composition as measured by NGS and the importance of considering temporal effects in future applications of NGS to identify microbial pollution sources. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Article
Culturable enterococci and a suite of environmental variables were collected during a predominantly dry summer at a beach impacted by nonpoint source pollution. These data were used to evaluate sands as a source of enterococci to nearshore waters, and to assess the relationship between environmental factors and dry-weather enterococci abundance. Best-fit multiple linear regressions used environmental variables to explain more than half of the observed variation in enterococci in water and dry sands. Notably, during dry weather the abundance of enterococci in dry sands at the mean high-tide line was significantly positively related to sand moisture content (ranging from <1-4%), and the daily mean ENT in water could be predicted by a linear regression with turbidity alone. Temperature was also positively correlated with ENT abundance in this study, which may indicate an important role of seasonal warming in temperate regions. Inundation by spring tides was the primary rewetting mechanism that sustained culturable enterococci populations in high-tide sands. Tidal forcing modulated the abundance of enterococci in the water, as both turbidity and enterococci were elevated during ebb and flood tides. The probability of samples violating the single-sample maximum was significantly greater when collected during periods with increased tidal range: spring ebb and flood tides. Tidal forcing also affected groundwater mixing zones, mobilizing enterococci from sand to water. These data show that routine monitoring programs using discrete enterococci measurements may be biased by tides and other environmental factors, providing a flawed basis for beach closure decisions.
Article
Forced by tides and waves, large volumes of seawater are flushed through the beach daily. Organic material and nutrients in seawater are remineralized and cycled as they pass through the beach. Microorganisms are responsible for most of the biogeochemical cycling in the beach, however, few studies have characterized their diversity in intertidal sands, and little work has characterized the extent to which microbes are transported between different compartments of the beach. The present study uses next generation massively parallel sequencing to characterize the microbial community present at 49 beaches along the coast of California. In addition, we characterize the transport of microorganisms within intertidal sands using laboratory column experiments. We identified extensive diversity in the beach sands. Nearly 1000 unique taxa were identified in sands from 10 or more unique beaches suggesting the existence of a group of 'cosmopolitan' sand microorganisms. A biogeographical analysis identified a taxa-distance relationship among the beaches. In addition, sands with similar grain size, organic carbon content, exposed to a similar wave climate, and having the same degree of anthropogenic influence tended to have similar microbial communities. Column experiments identified microbes readily mobilized by seawater infiltrating through unsaturated intertidal sands. The ease with which microbes were mobilized suggests intertidal sands may represent a reservoir of bacteria that seed the beach aquifer where they may partake in biogeochemical cycling.