Influence of Land Use, Nutrients, and Geography on Microbial Communities and Fecal Indicator Abundance at Lake Michigan Beaches

Abstract

bMicrobial communities within beach sand play a key role in nutrient cycling and are important to the nearshore ecosystem function. Escherichia coli and enterococci, two common indicators of fecal pollution, have been shown to persist in the beach sand, but little is known about how microbial community assemblages are related to these fecal indicator bacteria (FIB) reservoirs. We examined eight beaches across a geographic gradient and range of land use types and characterized the indigenous community structure in the water and the backshore, berm, and submerged sands. FIB were found at similar levels in sand at beaches adjacent to urban, forested, and agricultural land and in both the berm and backshore. However, there were striking differences in the berm and backshore microbial communities, even within the same beach, reflecting the very different environmental conditions in these beach zones in which FIB can survive. In contrast, the microbial communities in a particular beach zone were similar among beaches, including at beaches on opposite shores of Lake Michigan. The differences in the microbial communities that did exist within a beach zone correlated to nutrient levels, which varied among geographic locations. Total organic carbon and total phosphorus were higher in Wisconsin beach sand than in beach sand from Michigan. Within predominate genera, finescale sequence differences could be found that distinguished the populations from the two states, suggesting a biogeographic effect. This work demonstrates that microbial communities are reflective of environmental conditions at freshwater beaches and are able to provide useful information regarding long-term anthropogenic stress. Since the creation of the Federal Beach Environmental Assessment and Coastal Health (BEACH) Act of 2000, coastal communities have been challenged with implementing programs for the monitoring of recreational waters. Water quality monitoring relies on fecal indicator bacteria (FIB), such as Escherichia coli and enterococci, and the assumption that both are fecal in origin. In recent years, many Great Lakes coastal recreational waters were monitored for the first time and subsequently were found to have unacceptable levels of E. coli, indicating the presence of contamination from sources such as sewage, stormwater, or agricultural runoff. However, recent studies have detected high concentrations of FIB in recreational beach sands compared to the concentrations in the nearby monitored waters (1-4). Importantly, several studies have documented that sand reservoirs of FIB play a large role in beach water samples exceeding regulatory limits (1, 3, 5-7).Persistent FIB in the beach environment is of great concern. The presence of FIB in either recreational waters or sand is assumed to indicate a recent pollution event. However, the persistence and possible proliferation of FIB in the beach environment can confound beach-monitoring efforts and poses additional challenges for beach managers. In addition, there is mounting evidence that E. co...

Distribution and Differential Survival of Traditional and Alternative Indicators of Fecal Pollution at Freshwater Beaches

“…Beach sand samples were analyzed using the Gull2, Lachno2, and HB assays. Selected water and sand samples that were collected from either Point Beach State Park or Kohler-Andrae State Park were also analyzed using the ruminant-specific BacR assay due to the proximal agricultural land use practices (14).…”

“…Although recreational waters are the primary monitoring focus for beach managers, numerous studies have documented high concentrations of fecal indicators within beach sand (12,14,32). Recent research has reported the recovery of bacterial and viral human pathogens from beach sand, providing evidence that sand contact may play an important role in beach-associated gastrointestinal (GI) illness (33)(34)(35).…”

“…Due to their ubiquitous nature in warm-blooded animals (7)(8)(9), fecal indicators can only indicate that fecal contamination may be present; however, certain host sources are more likely than others to carry human pathogens (10). Additionally, E. coli, the most commonly used indicator in freshwater systems, has been found to survive in the environment (11)(12)(13)(14). Environmental persistence of fecal indicator bacteria undermines the utility for recreational water quality monitoring because the presence of these organisms would not necessarily indicate a recent contamination event, and in some cases, it can lead to an overestimation of the associated public health risk.…”

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

“…To date, nearly all of the next-generation sequencing studies of sands have focused on sand from marine beaches (2,3,(31)(32)(33)(34)(35), but one recent study has focused on sand from freshwater beaches (17), and due to differences in methodology, including the sequencing platform and biases associated with the sequencing region associated with primer targets (36), the ability to compare these data sets with each other has been limited. In this study, beach sands from 11 beaches throughout the United States, Japan, and South Korea, including 4 beaches from the Great Lakes, were extensively characterized by using Illumina next-generation sequencing of the 16S rRNA gene.…”

“…Recently, bacterial communities in beach sands have begun receiving increasing attention due to their relevance to public health (4,(13)(14)(15)(16)(17)(18). While recreational waters have long been monitored for indicators of human fecal pollution and their presumed indication of risk to humans because of the presence of human pathogens (19,20), beach sands have historically been neglected in this area.…”