Creating a microcosm to examine salinity tolerance of Escherichia coli in beach sand

Escherichia coli (E. coli) is a bacteria species that thrives in a variety of environments. Due to its widespread prevalence, it is commonly used as an indicator for pollution and other pathogens. One place where it is not often looked for is oceanic beaches because E. coli is inhibited by salt. However, recent research has shown that E. coli often thrives in sand at beaches. To determine how it persists in sand, we created a microcosm simulating the intertidal zone of a beach. Using this microcosm, we are testing how varying salinity levels affect persistence of E. coli in sand. Collectively, our findings suggest that E. coli may be able to persist on sandy beaches despite the stress of salinity and may be a useful tool in the future for assessing these ecosystems for fecal contamination levels

Creating a microcosm to examine salinity tolerance of \u3cem\u3eEscherichia coli\u3cem\u3e in beach sand

Escherichia coli (E. coli) is a gram-negative bacteria species that thrives in a variety of environments around the world. Due to its widespread prevalence, it is commonly used as an indicator for fecal pollution and other pathogens. One place where it is not often looked for is oceanic beaches because E. coli is inhibited by salt. However, recent research has shown that E. coli often thrives in sand at many oceanic beaches. To determine how it persists in sand, we created a microcosm simulating the intertidal zone of an oceanic beach. Using this microcosm, we examined how varying levels of salinity (0-6%) affect the persistence of E. coli in these sandy environments. We found that there was a negative correlation between increasing salinity and the most probable number of E. coli colony forming units, which suggests that E. coli is being inhibited by salinity to a degree. However, we still found that E. coli was able to persist at all salt concentrations including those that exceed normal oceanic salinity. Collectively, our findings suggest that E. coli may be able to persist on sandy beaches despite the stress of salinity and may be a useful tool in the future for assessing thes

Creating a Microcosm to Examine Salinity Tolerance of \u3cem\u3eEscherichia coli\u3c/em\u3e in Beach Sand

Escherichia coli (E. coli) is a gram-negative bacteria species that thrives in a variety of environments around the world. Due to its widespread prevalence, it is commonly used as an indicator for fecal pollution and other pathogens. One place where it is not often looked for is oceanic beaches because E. coli is inhibited by salt. However, recent research has shown that E. coli often thrives in sand at many oceanic beaches. To determine how it persists in sand, we created a microcosm simulating the intertidal zone of an oceanic beach. Using this microcosm, we examined how varying levels of salinity (0-6%) affect the persistence of E. coli in these sandy environments. We found that there was a negative correlation between increasing salinity and the most probable number of E. coli colony forming units, which suggests that E. coli is being inhibited by salinity to a degree. However, we still found that E. coli was able to persist at all salt concentrations including those that exceed normal oceanic salinity. Collectively, our findings suggest that E. coli may be able to persist on sandy beaches despite the stress of salinity and may be a useful tool in the future for assessing these ecosystems for fecal contamination levels

Salinity Tolerance and Survival of Laboratory and Environmental Strains of Escherichia coli

Escherichia coli are commonly utilized as fecal indicators to assess contamination and water quality in a variety of ecosystems. One group of ecosystems of particular interest is sandy beaches, which are exposed to varying stressors from both terrestrial and marine sources. Historically, beach ecosystems were not thought to be ideal habitats for E. coli because salinity can inhibit growth and survival of these bacteria. However, recent studies have demonstrated that certain strains may be able to persist in these environments. Here, we expand upon this recent research and test the effects of salinity on the survival and growth of a laboratory strain of E. coli, as well as environmental strains collected from sand samples at Folly Beach, South Carolina. We exposed our strains of E. coli to salt concentrations ranging from 0.5-10 % and assessed the colony forming units (CFUs) following each of our treatments after a period of 24 hours at 37 °C. Our data indicated there was a significant decrease in CFUs and a noticeable reduction in diameter of colony size as salinity increased. In addition, we observed that there is a cut-off for salinity tolerance, as no colonies were able to grow in salinity concentrations greater than 5 %. Collectively, our findings suggest that E. coli can persist on sandy beaches despite the stress of salinity and may be a useful tool in the future for assessing these ecosystems for fecal contamination levels

Water Quality and Biomonitoring in the Río Lagarto, Costa Rica

Every odd-year in March, from 2005-2015, the Río Lagarto, Costa Rica has been surveyed by students in Tropical Watersheds and Coastal Ecology. The Río Lagarto originates at approximately 1,500 m in the Monteverde cloudforest region of the Cordillera de Tilarán and steeply descends toward the Pacific coast discharging into the mangrove forests bordering the Gulf of Nicoya. This small Pacific slope river is the western-most of the three rivers, along with their watersheds, that define the Bellbird Biological Corridor. The Bellbird Biological Corridor is a long-term community-based effort to restore natural forest cover to a largely deforested terrain. This reforestation and ecological restoration effort is meant to insure that migratory animals, and the bellbird being used as the symbolic representation for the corridor, have adequate habitat from high-altitude cloud forest to lowland deciduous forest habitat for their sustainable survival. Along the Río Lagarto, water samples were collected from five sites that were characterized by their elevation, canopy coverage, and relation to places of human occupation. Physical, chemical, and nutrient analyses assessed, mainly in situ, were water temperature, dissolved oxygen (DO), pH, conductivity, turbidity, salinity, nitrogen and phosphorus. Total nitrogen and total phosphorus were analyzed upon return in the Winthrop Ecology Laboratory. Lacking local water quality criteria, or standards, for comparison, we used South Carolina water quality criteria (SCDHEC) where possible. Based on SCDHEC criteria, DO was satisfactory except for 2009 and pH levels were normal. Due to variable elevations among the sites, water temperature increased from the upper to lower watershed. Concerning conductivity, it only substantially increased near the mangrove forest due to the influence of saline water from the Gulf of Nicoya. Turbidity was low as expected in the dry season of a typical March without any substantial runoff from the adjacent land. Concerning nutrient analysis, ammonia concentrations did not reveal much information about sewage or agricultural run-off. However, a high phosphate level was observed in 2005 in the upper watershed sampling site; this may be a direct result of runoff from a nearby dairy farm. The highest levels of nitrate were also found at this site based on lab analysis. From year to year, total phosphorous levels were consistently high (above SCDHEC criteria). While an increasing trend was not observed, 2013 had higher total phosphorus levels compared to earlier years. Total nitrogen levels were not excessive except for a value of 8.2 mg/L at the mid-watershed site in 2009. In addition to water quality parameters, biomonitoring was conducted via the collection of macroinvertebrates at the three upper and mid-watershed sites that were accessible on foot. Presence specifically of the aquatic stages of three common insect orders, Mayflies (Ephermeroptera), Stoneflies (Plecoptera) and Caddisflies (Trichoptera) suggest that water quality was satisfactory. In summary, while overall water quality was relatively good and stable over the 10-year period of study, an excess of nutrients, especially phosphorus, was a concern. Although the region is deforested, good water quality may be a result of low population density and the rural setting. In order to maintain water quality and improve the degraded shoreline and embankments, the creation of a wide riparian buffer zone along the Río Lagarto should be considered to reach the goals of the Bellbird Biological Corridor