Week of July 31 - August 6, 2022
Water Column Profiles
Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries using a Seabird profiling instrument on August 3, 2022. Light rainfall of 0.11 inches was recorded at T.F. Green two days prior to the survey. Evidence of density stratification was observed at most sites, while the water column at Point St. Bridge and Pomham Rocks was more well-mixed.
Salinity was lowest this week at Phillipsdale Landing, averaging approximately 24 psu at the surface and 26 psu at the bottom. Salinity was highest at Bullock Reach Buoy and Conimicut Point, averaging 29 psu at the surface and 31 psu at the bottom. These two sites had the coldest waters, averaging 25°C at the surface and 22-23°C at the bottom. The warmest water temperatures (29-30°C) were observed at Point St. Bridge.
Overall, dissolved oxygen (DO) was low in the bottom waters at most sites this week, with three sites exhibiting hypoxic conditions (DO <2.9 mg/L) below 4 m depth. India Point Park waters had minimum readings around 1.0 mg/L; Phillipsdale Landing minimum readings were 2.1 mg/L; Edgewood Yacht Club minimum readings were 2.8 mg/L. Fluorescence was similar to the previous week, with the highest values (16.7 mg/m3) observed near the surface (~0.75 m) at Pawtuxet Cove. Please note: numerical fluorescence data were not posted from 2020 to 2021 due to a QC issue. This issue has been resolved and fluorescence data from 2020 and 2021 will be back-filled.
Week of September 4 - 10, 2022
Phytoplankton Sampling
Phytoplankton samples were collected on September 7, 2022 at Bullock Reach and analyzed in the laboratory shortly after collection. It was cloudy on Narragansett Bay with choppy waters and strong northeast winds. Sondes data revealed the surface water temperature was 22.17⁰C, salinity was 20.43 psu, and chlorophyll a was 0.39 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a medium brown color and had a medium filter time. The tow net sample was analyzed qualitatively for microorganisms using phase contrast microscopy. The whole water sample was analyzed quantitatively under 200x phase contrast microscopy. A Hensen Stempel pipette was used to accurately deliver 1ml of sample to a Sedge-wick Rafter chamber. This analysis revealed a total of 858,000 cells per Liter. The microflagellates were found at 814,000 cells/L. The most predominant phytoplankton genus was Chaetoceros spp. at 18,000 cells/L. Other representative genera include Skeletonema spp. and Leptocylindrus spp.
200x phase contrast micrograph of diatom Dictoycha spp.
Week of September 11 - 17, 2022
Bacteria Sampling
On September 14, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers. Five of these stations were also sampled for enterococci bacteria. Precipitation in the five days prior to sampling totaled 0.68 inches as recorded at TF Green.
Overall, bacteria counts were higher this week than during the previous sampling event on August 31. The geometric mean of fecal coliform results for all sites was 267 MPN/100 mL, with the Seekonk River sites having higher counts than the Providence River sites (geometric means of 1162 MPN/100 mL and 134 MPN/100 mL, respectively). The maximum count (4300 MPN/100 mL) was measured at Phillipsdale Landing in the Seekonk River, and Point St. Bridge and Collier Point Park in the Providence River.
Enterococci results had an overall geometric mean of 44 MPN/100 mL. Enterococci results ranged from non-detect at Conimicut Point (duplicate sample) to 384 MPN/100 mL at the Point St. Bridge site.
The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of water ingestion (e.g., swimming, diving, water skiing, and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.
Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing
| Fecal Coliform | Enterococci |
| Primary Contact1 | Geometric mean ≤50 MPN/100 mL
<10% of samples >400 MPN/100 mL
| Geometric mean ≤35 colonies/100 mL
All samples ≤104 colonies/100 mL2 |
| Shellfishing | Geometric mean ≤14 MPN/100 mL
<10% of samples >49 MPN/100 mL3 | NO ENTEROCOCCI CRITERIA
|
1Fecal coliform primary contact criteria applied only when adequate enterococci data are not available;
2Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health;
3For a three-tube decimal dilution
Week of July 24 - 30, 2022
Nutrients Sampling
Nutrient samples were collected from seven local river stations, and eight bay stations on July 27, 2022. The Edgewood Shoal bay station was sampled at surface and bottom while all other bay stations were only sampled at the surface. In the five days prior to sampling, there was no precipitation recorded at T.F. Green.
Among the river stations sampled, the highest total nitrogen (TN) was observed at Pawtuxet River at Broad Street as 1480 ppb. The highest total dissolved nitrogen (TDN) and dissolved inorganic nitrogen (DIN) were observed at Blackstone River at Slater Mill. The TDN and DIN were 1,240 ppb and 810.4 ppb respectively. The lowest TN (689 ppb) was observed in one of duplicate samples collected at the Ten Mile River at Roger Williams Ave. site; the duplicate was higher at 793 ppb. Both duplicates were low in DIN, averaging 269.4 ppb, the lowest of all sites sampled this day. The lowest TDN (625 ppb) was observed at Moshassuck River at Higginson Ave.
Among the bay stations sampled, the highest TN (1,050 ppb) was observed at Phillipsdale Landing; its duplicate was 1,020 ppb. Pawtuxet Cove was similarly high at 1,030 ppb. The highest TDN and DIN were observed at Pawtuxet Cove as 671 ppb and 435.3 ppb respectively. The lowest surface TN (582 ppb), TDN (219 ppb) and DIN (13 ppb) were observed at Conimicut Point. Chlorophyll a concentrations at the bay stations increased from the previous sampling event, averaging 21.0 ug/L across all sites. The maximum result (47.63 ug/L, average of duplicates) occurred at Phillipsdale Landing.
Results from nutrient sampling on August 9-10, August 24, and September 7 are pending analysis. The next scheduled sample date is September 21.
Week of July 10 - 16, 2022
Nutrients Sampling
Nutrient samples were collected from thirteen local and border river stations and one bay station (Phillipsdale Landing) on July 13, 2022; an additional six bay stations were sampled on July 14, 2022. Bay sampling was delayed due to a small craft advisory in Narragansett Bay. Each of the bay stations were sampled at the surface and bottom. In the five days prior to sampling, there were trace amounts of precipitation recorded at T.F. Green.
Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Coles River at Milford Road. At this site, TN, TDN and DIN were 1,530 ppb, 1,580 ppb, and 1,321 ppb respectively. The lowest TN (549 ppb) was observed in the samples Moshassuck River at Higginson Ave. The lowest TDN (323 ppb, average of duplicates) and lowest DIN (30 ppb, average of duplicates) were observed at the Taunton River at Berkley Bridge.
Among the bay stations sampled, the highest surface TN was observed in the samples from Pawtuxet Cove. Duplicate samples at this site averaged 1,125 ppb TN, 1,015 ppb TDN, and 752 ppb DIN. The lowest surface TN (376 ppb), TDN (174 ppb) and DIN (13 ppb) were observed at Conimicut Point. Chlorophyll a concentrations at the bay stations decreased from the previous sampling event, averaging 6.85 ug/L across all sites. The maximum result of 11.97 ug/L occurred at Bullock Reach Buoy.
Results from nutrient sampling on July 27, August 9-10, and August 24 are pending analysis. The next scheduled sample date is September 7.
