Surface chlorophyll data were collected on July 26, 2023 while the R/V Monitor was underway collecting nutrient samples in the Providence and Seekonk River estuaries. The average chlorophyll concentrations were categorized as good in the Seekonk River and as fair in all other areas. Overall, chlorophyll ranged from 2.18 to 29.09 µg/L with an average of 9.37 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.
Phytoplankton samples were collected on July 26, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. Sondes data revealed the surface water temperature was 25.586⁰C, salinity was 16.22psu, and chlorophyll a was 19.77 ug/L. It was a hot and humid day with calm conditions on Narragansett Bay. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light tan color and had a quick filter time. Some small comb jellies were detected. 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 462,000 cells per Liter. The micro flagellates were found at 376,000 cells/L. The most predominant phytoplankton genus was Heterocapsa spp. at 38,000 cells/L. Other representative genera include Guinardia spp., Thalassiosira spp., and Eutreptiella spp.
Nutrient samples were collected from 14 river stations and 8 bay stations on July 26th. Edgewood Shoal was sampled at the surface and bottom; all other bay stations were sampled at the surface only. In the five days prior to sampling, there were 0.47 inches of rainfall recorded at T.F. Green.
Among the river stations sampled, the highest total nitrogen (TN) and total dissolved nitrogen (TDN) concentrations were observed at Ten Mile River @ Central Ave. (TN = 1,470 ppb, TDN = 1,550 ppb); the highest dissolved inorganic nitrogen (DIN) concentration was observed at Pawtuxet River @ Broad St. (1,120 ppb). The lowest TN and TDN were observed at Moshassuck River @ Footbridge at Mill St. (TN = 654 ppb, TDN = 688 ppb, average of duplicates), while the lowest DIN was at Coles River @ Milford Rd. (147 ppb).
Among the bay stations sampled, the highest surface TN was observed at Pomham Rocks (989 ppb), the highest surface TDN was observed at Phillipsdale Landing (940 ppb), and the highest surface DIN was observed at Pawtuxet Cove (679 ppb). The lowest surface TN was observed at India Point Park (TN = 731 ppb), while the lowest surface TDN and DIN were at Bullock Reach Buoy (TDN = 230 ppb, DIN = 24.0 ppb). Chlorophyll a concentrations at the surface bay stations were moderately elevated this week; concentrations averaged 14.5 μg/L overall with a maximum of 26.4 μg/L at Bullock Reach Buoy.
The next scheduled sampling date is August 8, 2023.
Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on July 26, 2023 using a Seabird Electronics profiler. In the three days leading up to the survey, there were 0.10 inches of precipitation recorded at T.F. Green. Moderate density stratification was observed at Edgewood Shoal; all other sites still exhibited strong stratification this week.
Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the middle and/or lower half of the water column at all sites surveyed. Fluorescence was moderately elevated at the surface of most sites this week, but relatively low at Phillipsdale Landing and India Point Park.
Nutrient samples were collected from 14 river stations and 8 bay stations on July 26th. Edgewood Shoal was sampled at the surface and bottom; all other bay stations were sampled at the surface only. In the five days prior to sampling, there were 0.47 inches of rainfall recorded at T.F. Green.
Among the river stations sampled, the highest total nitrogen (TN) and total dissolved nitrogen (TDN) concentrations were observed at Ten Mile River @ Central Ave. (TN = 1,470 ppb, TDN = 1,550 ppb); the highest dissolved inorganic nitrogen (DIN) concentration was observed at Pawtuxet River @ Broad St. (1,120 ppb). The lowest TN and TDN were observed at Moshassuck River @ Footbridge at Mill St. (TN = 654 ppb, TDN = 688 ppb, average of duplicates), while the lowest DIN was at Coles River @ Milford Rd. (147 ppb).
Among the bay stations sampled, the highest surface TN was observed at Pomham Rocks (989 ppb), the highest surface TDN was observed at Phillipsdale Landing (940 ppb), and the highest surface DIN was observed at Pawtuxet Cove (679 ppb). The lowest surface TN was observed at India Point Park (TN = 731 ppb), while the lowest surface TDN and DIN were at Bullock Reach Buoy (TDN = 230 ppb, DIN = 24.0 ppb). Chlorophyll a concentrations at the surface bay stations were moderately elevated this week; concentrations averaged 14.5 μg/L overall with a maximum of 26.4 μg/L at Bullock Reach Buoy.
The next scheduled sampling date is August 8, 2023.
Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on July 26, 2023 using a Seabird Electronics profiler. In the three days leading up to the survey, there were 0.10 inches of precipitation recorded at T.F. Green. Moderate density stratification was observed at Edgewood Shoal; all other sites still exhibited strong stratification this week.
Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the middle and/or lower half of the water column at all sites surveyed. Fluorescence was moderately elevated at the surface of most sites this week, but relatively low at Phillipsdale Landing and India Point Park.
On July 19, 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 3.96 inches as recorded at TF Green, most of which occurred on July 16.
The geometric mean of fecal coliform results for all sites was 463 MPN/100 mL compared to 3472 MPN/100 mL on July 5. Overall, bacteria counts were lower in both the Seekonk and Providence Rivers this week than during the previous sampling event on July 5. Fecal coliform counts were geomeans of 289 MPN/ 100 mL in the Seekonk River and 578 MPN/ 100 mL in the Providence River. The maximum count (9300 MPN/100 mL) was measured at Point St. Bridge in the Providence River.
Enterococci results had an overall geometric mean of 26 MPN/100 mL. Enterococci counts ranged from non-detect at a Phillipsdale Landing duplicate to 158 MPN/100 mL at Point St. Bridge.
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 ingesting water (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
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
Surface chlorophyll data were collected on July 19, 2023 while the R/V Monitor was underway collecting bacteria samples in the Providence and Seekonk River estuaries. The average chlorophyll concentrations were categorized as good in the Seekonk River and Northern Providence River Channel and as fair in the Pawtuxet River, Edgewood Shoals, and Southern Providence River areas. Overall, chlorophyll ranged from 1.26 to 24.06 µg/L with an average of 7.04 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.
Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on July 19, 2023 using a Seabird Electronics profiler. In the three days leading up to the survey, there were 3.35 inches of precipitation recorded at T.F. Green. Strong density stratification was observed at all sites surveyed this week.
Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the middle and/or lower half of the water column at all sites surveyed. Fluorescence was moderately elevated at the surface of Conimicut Point West, Edgewood Yacht Club, and Bullock Reach Buoy this week and relatively low at the other sites.
Water clarity was measured at six locations in the Providence River and Seekonk River estuaries on July 12. Rainfall totaling 1.91 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 1.0 meters, compared to 1.1 meters on the previous survey (July 5). The lowest clarity this week (0.6 meters) was measured at Pawtuxet Cove while the greatest clarity (1.6 meters) was measured at India Point Park. There was a general north-to-south gradient of decreasing water clarity among the sites this week.
