Fecal indicator bacteria (FIB) levels during dry weather from Southern California reference streams

Abstract

High levels of fecal indicator bacteria (FIB) in surface waters is a common problem in urban areas that often leads to impairment of beneficial uses such as swimming. Once impaired, common management and regulatory solutions include development of total maximum daily loads (TMDLs) and other water quality management plans. A critical element of these plans is establishment of a "reference" level of exceedances against which to assess management goals and TMDL compliance. The goal of this study was to provide information on indicator bacteria contributions from natural streams in undeveloped catchments throughout southern California during dry weather, non-storm conditions. To help establish a regional reference data set, bacteria levels [i.e. Escherichia coli (E. coli), enterococci and total coliforms] were measured from 15 unimpaired streams in 11 southern California watersheds weekly for one full year. Concentrations measured from reference areas were typically between one to two orders of magnitude lower than levels found in developed watersheds. Nearly 82% of the time, samples did not exceed daily and monthly bacterial indicator thresholds. E. coli had the lowest daily percent exceedance (1.5%). A total of 13.7% of enterococci exceeded daily thresholds. Indicator bacteria levels fluctuated seasonally with an average of 79% of both enterococci and total coliforms exceedances occurring during summer months (June to August). Temperature, at all sites, explained about one-half the variation in total coliforms density suggesting that stream temperatures regulated bacterial populations. Accounting for natural background levels will allow for management targets that are more reflective of the contributions from natural sources.

The Impact of Environmental Variables on Faecal Indicator Bacteria in the Betna River Basin, Bangladesh

“…The frequent violation of water quality standards has also been reported in other studies (Noble et al 2003;Schilling et al 2009;Myers and Ambrose 2015). Enterococci concentrations were higher than E. coli concentrations in most of our samples, and this is also in agreement with previous studies (Shergill and Pitt 2004;Tiefenthaler et al 2009). The observed higher levels of enterococci are explained by enterococci's longer survival than E. coli in surface water (Liu et al 2006).…”

“…Therefore, the observed positive correlation with water temperature does not mean that temperature stimulated the increased FIB level in the study area. In some other studies FIB growth was suspected to be a possible reason for the positive relation between temperature and FIB (Byappanahalli et al 2003;Tiefenthaler et al 2009;Hong et al 2010;Abia et al 2015), for instance because of decreased dissolved oxygen content, algal blooms and nutrient richness (Rouf et al 2012). However, we have not found proof of FIB growth in the literature.…”

“…However, few studies reported positive correlation between water temperature and bacterial concentrations due to coincidence of summer temperature and periods of intense precipitation and high discharge (Koirala et al 2008;Schilling et al 2009). Some studies also reported the likelihood of some bacterial growth in tropical temperatures (Winfield and Groisman 2003;Tiefenthaler et al 2009). However, the net contribution of environmental variables (temperature, precipitation and salinity) to changes in pathogen concentrations is not clear (Vermeulen and Hofstra 2013).…”

Spatial and hydrologic variation of Bacteroidales, adenovirus and enterovirus in a semi-arid, wastewater effluent-impacted watershed

“…Compliance with recreational water quality (REC) criteria in 55 developed watersheds, both in the U.S. and elsewhere, represents a significant challenge to 56 responsible agencies, as a myriad of non-point bacteria sources contribute to impairment. Some 57 watersheds that are only subject to natural bacteria sources (e.g., birds) have been found to 58 exceed REC criteria (Tiefenthaler et al, 2008), and some waterbodies have been subject to 59 extensive remediation efforts yet exceedances of criteria persist (POLA, 2006). During storm 60 events in urbanized watersheds, which may represent >99% of the annual bacteria discharge 61 (Reeves et al, 2004), loading rates can be extraordinarily high -several times greater than the 62 equivalent daily fecal loading from the entire human population within the watershed (Surbeck et 63 In southern California, wet weather is traditionally defined as days with greater than 0.1 164 inches plus the three following days.…”

Assessing the impact of socio-economic development and climate change on faecal indicator bacteria in the Betna River, Bangladesh

“…These latter authors relate the positive correlation to the coincidence of high temperature and precipitation during summer period. In a few studies FIB growth was suspected to be a possible reason for the positive relationship between temperature and FIB (Byappanahalli et al, 2003, Tiefenthaler et al, 2009, Hong et al, 2010, Abia et al, 2015. Salinity was negatively correlated with pathogen concentrations (Hoppe et al, 2013, Dastager, 2015, Aragonés et al, 2016, Adingra et al, 2012.…”