September 11-17, 2023

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

 ​​Fecal Coli​fo​rmEnterococci
Primary Con​​​t​a​c​t1​​​​​Geom​e​tric me​a​n​ ≤50 MPN/1​​00​ mL
<10% ​o​f​​ samples >400 MPN/100 ​mL		Geom​etric mean ≤35 colo​nies/100 mL​
All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing​Geometric mean ≤14 MPN/100​ mL
<10% of samples >49 MPN/100 mL3​		NO ENTEROCOCCI C​​RITERIA

1Fecal coliform primary contact criteria app​lied 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

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

September 10-16, 2023

​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. 

September 3-9, 2023

​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.

September 3-9, 2023

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. 

August 28-September3, 2023

On August 31st, six stations were sampled for fecal coliform bacteria in the Providence River; one of these stations was also sampled for enterococci bacteria. There was a smaller set of stations sampled than normal due to weather conditions. Precipitation in the five days prior to sampling totaled 0.14 inches as recorded at TF Green. 

Overall, bacteria counts were higher in the Providence River this week than during the previous sampling event on August 16. The fecal coliform geomean for the Providence River was 110 MPN/100 mL this week. The maximum count (430 MPN/100 mL) was measured at the Save ​​the Bay site in the Providence River. 

Enterococci was only sampled at one site this week. Gaspee Point measured a non-detect enterococci count. 

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

 ​​Fe​cal Coli​fo​rmEnterococci
Primary Con​​​t​a​c​t1​​​​​Geom​e​tric me​a​n​ ≤50 MPN/1​​00​ mL
<10% ​o​f​​ samples >400 MPN/100 ​mL		Geom​etric mean ≤35 colo​nies/100 mL​
All sa​mples ≤104 colonies/100 ​​mL2
ShellfishingGeometric mean ≤14 MPN/100​ mL
<10% of samples >49 MPN/100 mL3​		NO ENTEROCOCCI CR​ITERIA

1Fecal coliform primary contact criteria app​lied 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

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

August 27-September 2, 2023

Surface chlorophyll data were collected on August 29, 2023 while the R/V Monitor was underway collecting nutrient samples in the Edgewood Shoals, Pawtuxet River and Southern Providence River areas (chlorophyll data were not collected for the Seekonk and Northern Providence River Channel areas due to data logging issues). The average chlorophyll concentrations were categorized fair in the areas surveyed. Overall, chlorophyll ranged from 5.57 µg/L to 12.80 µg/L with an average of 10.46 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

August 2023

​Phillipsdale Landing

The Phillipsdale Landing sondes have been deployed for the season since May 9th, 2023 utilizing a new setup allowing staff access to the equipment from the boat instead of standing on the dock. During the month of August, sondes were changed out for routine maintenance on August 1st, 16th, and 29th. 

Surface DO remained mostly above the hypoxia threshold, dropping briefly below the threshold for approximately an hour and a half on August 2nd and again on August 3rd. The bottom waters were hypoxic periodically throughout the month, with the longest sustained hypoxic periods (11 hours) occurring overnight between August 16th and 17th, and again overnight August 17th to 18th. DO averaged 6.4 mg/L at the surface with a minimum of 1.6 mg/L, while bottom waters averaged 3.0 mg/L with a minimum of 0.6 mg/L. 

Chlorophyll readings were generally low with intermittent periods of elevated readings through the month, suggestive of minor phytoplankton blooms. The surface and bottom readings averaged 4.3 µg/L and 4.1 µg/L, respectively. The maximum surface reading of 43.6 µg/L occurred on August 8th and the maximum bottom reading of 30.0 µg/L occurred on August 24th. 

Bullock Reach

The Bullock Reach buoy was deployed June 1st for the 2023 season. During the month of August, sondes were changed out for routine maintenance on August 8th and 22nd.

Surface DO remained above the hypoxia threshold all month. There were a few brief periods of hypoxic conditions in the middle waters, with the longest duration at 2 hours on August 18th. The bottom waters had hypoxic conditions on and off all month, with the longest sustained period of hypoxic conditions at 2.5 days between the 16th and 19th. Surface, middle, and bottom DO averaged 7.3 mg/L, 5.1 mg/L, and 3.5 mg/L, respectively.

Chlorophyll readings ranged from low to elevated, with evidence of moderate phytoplankton blooms occurring throughout the month. Readings averaged 13.8 µg/L at the surface, 11.1 µg/L at mid-depth, and 3.3 µg/L at the bottom. The maximum surface reading of 70.0 µg/L occurred on August 21st. Please note that data gaps occurred between the 1st and 2nd and between the 28th and 29th on the middle sonde due to equipment failure.​

August 20-26, 2023

​Surface chlorophyll data were collected on August 22, 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, Northern Providence River Channel, and Edgewood Shoals and as fair in all other areas. Overall, chlorophyll ranged from 1.56 to 44.70 µg/L with an average of 5.72 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

August 20-26, 2023

Phytoplankton samples were collected on August 23, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. Sonde data revealed the surface water temperature was 21.0°C and salinity was 26.5 psu. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light brown color and had a quick 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 1,866,000 cells per Liter. The micro flagellates were found at 348,000 cells/L. The most predominant phytoplankton genus was Leptocylindrus spp.at 948,000 cells/L. Other representative genera include Skeletonema spp., Chaetoceros spp. (see 200x phase contrast image below), and Guinardia spp.

August 13-19, 2023

​Water clarity was measured at five locations in the Providence River and Seekonk River estuaries on August 16. Rainfall totaling 0.61 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 2.8 meters, compared to 1.8 meters on the previous survey (August 9). The lowest clarity this week (1.9 meters) was measured at Phillipsdale Landing, while the greatest clarity (3.6 meters) was measured at Point St. Bridge. There was no clear north-to-south gradient in water clarity among the sites this week.

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