Landscape and seasonal factors influence Salmonella and Campylobacter prevalence in a rural mixed use watershed.

Salmonella and Campylobacter prevalence in stream networks of the Satilla River Basin (SRB) were monitored monthly from August 2007 to August 2009 to study relationships between these pathogens and land use, presence of poultry houses and wastewater treatment plant (WWTP) discharge. Salmonella and Campylobacter were detected at all 10 stream sites and the three sites at the sole wastewater treatment plant (WWTP) in the study area. In all, 43% (129/299) and 62% (96/156) of samples were positive for Salmonella and Campylobacter, respectively, with detection frequency increasing in downstream sites with more poultry production and influence of WWTP discharge. Both Salmonella and Campylobacter detection frequencies were positively associated with the number of poultry houses in the subwatersheds, but agricultural land use as a proportion of the watershed was not a significant predictor of either pathogen. Fecal indicator bacterial levels were assessed and evaluated for their ability to predict the presence of pathogens. Of those examined, enterococci was most predictive; of the 129 samples positive for Salmonella, 88% (113/129) were detected when enterococci were above EPA single sample threshold (61 CFU 100 ml(-1)); and of the 96 samples positive for Campylobacter, 90% (86/96) were detected when enterococci levels exceeded this level. Comparatively, Escherichia coli concentrations were above EPA single sample thresholds in 38% (49/129) of the positive Salmonella samples. Detection of the pathogens throughout the watershed indicated that there was potential for waterborne transmission especially in downstream areas that were more likely to have recreational users.

Geostatistical modeling of the spatial distribution of sediment oxygen demand within a Coastal Plain blackwater watershed.

Blackwater streams are found throughout the Coastal Plain of the southeastern United States and are characterized by a series of instream floodplain swamps that play a critical role in determining the water quality of these systems. Within the state of Georgia, many of these streams are listed in violation of the state's dissolved oxygen (DO) standard. Previous work has shown that sediment oxygen demand (SOD) is elevated in instream floodplain swamps and due to these areas of intense oxygen demand, these locations play a major role in determining the oxygen balance of the watershed as a whole. This work also showed SOD rates to be positively correlated with the concentration of total organic carbon. This study builds on previous work by using geostatistics and Sequential Gaussian Simulation to investigate the patchiness and distribution of total organic carbon (TOC) at the reach scale. This was achieved by interpolating TOC observations and simulated SOD rates based on a linear regression. Additionally, this study identifies areas within the stream system prone to high SOD at representative 3rd and 5th order locations. Results show that SOD was spatially correlated with the differences in distribution of TOC at both locations and that these differences in distribution are likely a result of the differing hydrologic regime and watershed position. Mapping of floodplain soils at the watershed scale shows that areas of organic sediment are widespread and become more prevalent in higher order streams. DO dynamics within blackwater systems are a complicated mix of natural and anthropogenic influences, but this paper illustrates the importance of instream swamps in enhancing SOD at the watershed scale. Moreover, our study illustrates the influence of instream swamps on oxygen demand while providing support that many of these systems are naturally low in DO.

Distribution and ecology of campylobacters in coastal plain streams (Georgia, United States of America).

Campylobacter is the leading cause of bacterium-associated diarrhea in the United States and most developed countries. While this disease is considered a food-borne disease, many clinical cases cannot be linked to a food source. In rural and agrarian areas environmental transmission may be an important factor contributing to case loads. Here we investigated the waterborne prevalence of campylobacters in a mixed-use rural watershed in the coastal plain of southern Georgia (United States). Six sites representing various degrees of agricultural and human influence were surveyed biweekly to monthly for 1 year for the presence of culturable thermophilic campylobacters and other measures of water quality. Campylobacters were frequently present in agriculture- and sewage-impacted stretches of streams. The mean campylobacter counts and overall prevalence were highest downstream from a wastewater treatment plant that handled both human and poultry slaughterhouse waste (