Historical News
Bacteria Sampling
Twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers on October 17, 2018; five of these stations were also sampled for enterococci bacteria. Five days prior to sampling, 1.23 inches of rainfall was recorded; however, rainfall was light (<0.15 in) in the three days prior to sampling.
Fecal coliform geometric mean results decreased from the previous sampling to 84 MPN/100 mL. Fecal coliform concentrations were higher in the Seekonk River (geometric mean: 168 MPN/100 mL) than in the Providence River (geometric mean: 61 MPN/100 mL). The Crook Point and Phillipsdale Landing sites had the highest fecal coliform results observed in the Seekonk River, at 430 MPN/100 mL. In the Providence River, the maximum fecal coliform concentration, 750 MPN/100 mL, was measured at Point St. Bridge. Results indicate both rivers exceeded primary contact and shellfishing standards.
The overall enterococci geometric mean was 33 MPN/100 mL. Concentrations ranged from approximately 10 MPN/100 mL at Conimicut Point and Gaspee Point to 246 MPN/100 mL at Point St. Bridge. Though the geometric mean of all sites was below state primary contact standards, enterococci results exceeded the single sample maximum primary contact standard at Point St. Bridge.
Please note: the results of NBC's fecal coliform and enterococci monitoring are for informational/research purposes only and are not intended to suggest official state compliance with bathing or shellfishing standards.
Water Column Profiles
Highest surface salinity, 23 psu, was observed at Bullock Reach, while highest bottom salinity, 29 psu, was observed at Conimicut Point. Water column salinity was lowest at Phillipsdale Landing, ranging from 3 psu at the surface to 22 psu at depth.
Surface water temperatures were highest at Point Street Bridge, ranging from 18.6°C at 0.75 m to 20.5°C at 1.5 m. Surface temperatures were lowest at Phillipsdale landing, at 13.3°C. Temperatures at depth were similar among sites, ranging from 18°C to 19°C.
Hypoxic conditions (DO <2.9 mg/L) were not present at any of the nine sites sampled. The maximum DO concentration (8.69 mg/L) was observed in surface waters at India Point Park, while the minimum DO concentration (3.66 mg/L) occurred at depth at Point Street Bridge. The maximum fluorescence, 3.22 mg/m3, was observed at a depth of 1.75 m at Conimicut Point.
Water Column Profiles
Salinity ranged from 18.8 psu at the surface to 27.8 psu at depth at Edgewood Shoal. The water column at Pomham Rocks exhibited a similar gradient of low surface salinity to higher bottom salinity, with values ranging from 19.4 psu to 26.5 psu.
Water temperatures were highest at the surface, measuring approximately 20.5°C at both sites. Temperatures at depth were 19.7°C and 19.5°C at Edgewood Shoal and Pomham Rocks, respectively.
Hypoxic conditions (DO <2.9 mg/L) were present at Edgewood Shoal below a depth of 5.25 m. At Pomham Rocks, DO ranged from 6.3 mg/L at the surface to 4.2 mg/L in bottom waters. The maximum fluorescence, 3.98 mg/m3, was observed in surface waters (0.5 m depth) at Pomham Rocks.
R/V Monitor's Blog
On Wednesday, October 24th, the crew of the R/V Monitor was out on the upper Bay collecting nutrients and plankton samples, taking Secchi Disk and Par sensor water clarity measurements, conducting water column profiles using the Seabird instrument, and conducting real-time surface mapping of water quality parameters, including dissolved oxygen, chlorophyll, water temperature, salinity, and pH, all in an effort to document water quality improvements associated with NBC construction projects. Jeff captained the boat while monitoring professionals Mike and Fern collected the samples and data. NBC also assisted a URI-GSO researcher retrieve monitoring devices used to obtain current data for the ROMS hydrodynamic model of Narragansett Bay. It was a cool raw day with very little sunshine and dark clouds. The waters were calm in the morning, but the wind picked up from the northwest and the waters became choppy by the afternoon. Below is a photo of the Seabird profiling instrument being readied for deployment.
Water Column Clarity
Water clarity was measured at four locations on October 24, 2018. Approximately 0.2 inches of rainfall were recorded in the three days prior to the survey, and water clarity was lower than the previous week. The overall average Secchi depth of the four sites was 2.73 m. One site exhibited slightly higher clarity than the previous week (Pomham Rocks), while clarity declined at the remaining three sites. The lowest clarity overall was 2.43 m at Edgewood Yacht Club. The highest was 3.03 m at Conimicut Point. There was a weak gradient in increasing clarity with distance down bay.
