Phytoplankton samples were collected on September 20, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. Sonde data revealed the surface water temperature was 19.3°C, salinity was 24.5 psu, and chlorophyll a was 12.2 ug/L. The plankton tow net filtrate was a light brown color and had a long filter time. High particulates and comb jelly fish were detected. The whole water sample was analyzed and revealed a total of 76,000 cells per Liter. The micro flagellates were found at 28,000 cells/L. The most predominant phytoplankton genus was Leptocylindrus spp.at 27,000 cells/L. Other representative genera include Skeletonema spp. and Chaetoceros spp. Today’s featured micrograph shows a centric diatom at 400x phase contrast.
On September 14th, twenty stations were sampled for fecal coliform bacteria in the Providence River and Seekonk River; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, precipitation totaled 1.23 inches as recorded at TF Green.
Overall, bacteria counts were elevated this week. Fecal coliform counts were higher in the Seekonk River sites than in the Providence River sites (geometric means of 6,012 MPN/100 mL and 965 MPN/100 mL, respectively). The maximum count (24,000 MPN/100 mL) was measured at Crook Point.
Enterococci results had an overall geometric mean of 528 MPN/100 mL. Enterococci counts ranged from 85 MPN/100mL at Conimicut Point to 2,987 MPN/100 mL at Phillipsdale Landing.
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
Nutrient samples were collected from 14 river stations and 8 bay stations on September 20th, 2023. 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 1.55 inches of rainfall recorded at T.F. Green with the majority accumulated during a heavy rain event on September 18th.
Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) concentrations were observed at Ten Mile River at Roger Williams Ave. (TN = 1,305 ppb, TDN = 1,195 ppb, DIN = 771.5 ppb; all averaged with duplicates). The lowest TN and TDN were observed at Woonasquatucket River @ Valley St. (TN = 665 ppb, TDN = 635 ppb), while the lowest DIN was at Coles River @ Milford Rd. (DIN = 139.2 ppb).
Among the bay stations sampled, the highest surface TN, TDN, and DIN concentrations were observed at Pawtuxet Cove (TN = 1,120 ppb, TDN = 1,070 ppb, DIN = 638.3 ppb). The lowest surface TN was observed at Conimicut Point (TN = 799 ppb), while the lowest surface TDN and DIN were observed at Bullock Reach (TDN = 607 ppb, DIN = 300 ppb). Chlorophyll a concentrations at the surface bay stations averaged 2.8 μg/L overall with a maximum of 4.2 μg/L at Bullock Reach Buoy.
Surface chlorophyll data were collected on September 14, 2023 while the R/V Monitor was underway collecting nutrient samples in the Providence and Seekonk River estuaries. The average chlorophyll concentrations were categorized fair in the areas surveyed. Overall, chlorophyll ranged from 1.68 µg/L to 89.11 µg/L with an average of 9.02 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.
Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on November 30th, 2023. Rainfall totaling 0.69 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 4.5 meters, compared to 4.7 meters on the previous survey (November 15th). The lowest clarity this week (3.0 meters) was measured at Phillipsdale Landing, while the greatest clarity (5.5 meters) was measured at Bullock Reach. There was a general north-to-south gradient of increasing water clarity among the sites this week.
Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on November 15th, 2023. Trace amounts of rainfall was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 4.7 meters, compared to 3.0 meters on the previous survey (November 1st). The lowest clarity this week (3.4 meters) was measured at India Point, while the greatest clarity (5.8 meters) was measured at Conimicut Point. There was a general north-to-south gradient of increasing water clarity among the sites this week.
Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on October 25th, 2023. Rainfall totaling 1.14 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 3.6 meters, compared to 3.5 meters on the previous survey (October 18th). The lowest clarity this week (1.7 meters) was measured at Phillipsdale Landing, while the greatest clarity (6.1 meters) was measured at Bullock Reach. There was a general north-to-south gradient of increasing water clarity among the sites this week.
Surface chlorophyll data were collected on September 6, 2023 while the R/V Monitor was underway collecting nutrient samples in the Providence and Seekonk River estuaries. The average chlorophyll concentrations were categorized fair in the areas surveyed. Overall, chlorophyll ranged from 2.74 µg/L to 100.34 µg/L with an average of 13.59 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 September 6, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. Sonde data revealed the surface water temperature was 23.4°C, salinity was 24.5 psu, and chlorophyll a was 12.2 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light brown greenish color and had a long 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 2,856,000 cells per Liter. The micro flagellates were found at 108,000 cells/L. The most predominant phytoplankton genus was Leptocylindrus spp.at 2,196,000 cells/L. Other representative genera include Skeletonema spp., Chaetoceros spp., and Eucampia spp., the subject of the 200x phase contrast micrograph shown below.
Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on October 18th, 2023. There was trace amounts of precipitation recorded at TF Green in the five days prior to the survey. Secchi depth averaged 3.5 meters, compared to 2.9 meters on the previous survey (October 11th). The lowest clarity this week (2.4 meters) was measured at Phillipsdale Landing and India Point, while the greatest clarity (4.8 meters) was measured at Conimicut Point and Bullock Reach. There was a general north-to-south gradient of increasing water clarity among the sites this week.
