News – Page 3 – Narrabay

November 20, 2024

On November 20^th, 2024, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, no precipitation was recorded at TF Green. Overall, bacteria counts in both the Providence and Seekonk Rivers were lower compared to previous sampling (November 7^th, 2024).

Fecal coliform counts were higher in the Seekonk River sites than in the Providence River sites (geometric means of 14 MPN/100 mL and 9 MPN/100 mL, respectively). The maximum count (93 MPN/100 mL) was measured at Point St. Bridge.

Enterococci results had an overall geometric mean of 15 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 75 MPN/100 mL at Point St. Bridge.

The next scheduled sampling date is December 4th.

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 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

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

November 18, 2024

The Data Stream deployed on a chilly but otherwise beautiful November day. The team retrieved the Bullock’s Reach Sondes for the final time in the 2024 season. The buoy is scheduled to be removed from the water for the winter in early December. The picture below was taken while on route. In the distant background, accentuated by a rainbow, you can see the wind turbines from Johnson & Wales University and Narragansett Bay Commission’s Field’s Point Wastewater Treatment Facility.

November 7, 2024

Surface chlorophyll data were collected on November 7, 2024, while the R/V Monitor was underway collecting nutrient samples in the Providence and Seekonk River estuary. The average chlorophyll concentrations were categorized as good in all areas surveyed. Overall, chlorophyll ranged from 0.53 µg/L to 17.57 µg/L with an average of 2.89 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

October 30, 2024

Phytoplankton samples were collected on October 30, 2024 at Bullock’s Reach and analyzed in the laboratory shortly after collection. Weather conditions and Sonde data were not recorded on this day. The qualitative tow net sample had a moderate filtration time. The filtrate was slightly cloudy with some golden brown particulates. The analysis of the quantitative whole water sample revealed a total of 260,000 cells/L. The microflagellates were found at 100,000 cells/L. The most predominant phytoplankton genera were Chaetoceros spp. at 104,000 cells/L, Leptocylindrus spp. at 26,000 cells/L, and Skeletonema spp. at 18,000 cells/L. Proboscia alata, shown here in a 100x phase contrast micrograph, is a solitary or chain-forming diatom that can measure up to 1mm in length. They are identified by the presence of a proboscis with a truncated tip and offset claspers. These diatoms are an oceanic, temperate water species and are sometimes found near the coast.

October 30, 2024

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on October 30, 2024. In the five days prior to the survey, 0.03 inches of precipitation were recorded at TF Green. Secchi depth averaged 5.5 meters. The lowest clarity this week (2.9 meters) was measured at Phillipsdale Landing, while the greatest clarity (8.5 meters) was measured at Bullock Reach Buoy. There was a general north-to-south trend of increasing water clarity among the sites this week. Overall, water clarity increased from the previous measurements (data collected October 23, 2024).

October 9, 2024

The crew of the Data Stream were performing routine bacteria sampling when they observed two bald eagles flying high in the sky above the Seekonk River near Phillipsdale Landing in East Providence.

September 4, 2024

Nutrient samples were collected from seven river stations and seven bay stations on September 4th. All bay stations were sampled at the surface and bottom. In the five days prior to sampling, there was trace precipitation recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN) and total dissolved nitrogen (TDN) were observed at Blackstone River @ Stateline (TN = 1,340 ppb, TDN = 1,560 ppb). The highest dissolved inorganic nitrogen (DIN) concentration was observed at Moshassuck River @ Footbridge at Mill St. (1,158 ppb). The lowest TN and TDN were observed at Blackstone River @ Slater Mill (TN = 951 ppb, TDN = 958 ppb), while the lowest DIN was observed at Pawtuxet River @ Broad St. (665 ppb).

Among the bay stations sampled, the highest surface total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Pawtuxet Cove (TN = 963 ppb, TDN = 610 ppb, DIN = 368 ppb). The lowest surface TN and TDN were at Conimicut Point (TN = 456 ppb, TDN = 167 ppb, average of duplicates), while the lowest surface DIN concentrations were observed at Conimicut Point, Edgewood Yacht Club and Pomham Rocks (13 ppb, reflecting minimum detection limits).

The next scheduled sampling date is September 18, 2024.

August 7, 2024

Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on August 7, 2024 using a Seabird Electronics profiler. In the five days leading up to the survey, 0.95 inches of precipitation were recorded at T.F. Green. Water column stratification at the sites varied from weakly stratified at Pawtuxet Cove and Edgewood Yacht Club, to strongly stratified at Conimicut Point.

Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the lower portion of the water column at Edgewood Yacht Club, in the middle and lower portions of the water column at Pomham Rocks, and in all portions of the water column (upper, middle and lower) at India Point Park and Phillipsdale Landing. The highest fluorescence readings for the week were measured around 2 meters below the surface at Edgewood Yacht Club.

July 29-August 4, 2024

Phillipsdale Landing

Overall, water quality at Phillipsdale Landing was fair to poor this week. Weather conditions included sporadic rain events, with 1.16 inches of precipitation recorded at T.F. Green. The Blackstone River flow fluctuate through the week in response to rain, rising above the 19-year daily median mid-way through the week. Surface salinity averaged 17.8 ppt and ranged from 7.7 ppt to 24.4 ppt. At the bottom, salinity averaged 22.6 ppt and ranged from 14.3 ppt to 25.8 ppt. Temperatures continued to increase this week, averaging 25.5°C at the surface and ranging 23.4°C – 27.9°C. At the bottom, temperatures averaged 24.5°C and ranged 22.8°C – 26.8°C.

Dissolved oxygen (DO) at Phillipsdale Landing dropped below the hypoxia threshold (i.e., DO >2.9 mg/L) over the week. Surface DO average 6.5 mg/L and ranged from 0.8 mg/L to 17.3 mg/L. Bottom DO concentrations averaged 2.6 mg/L and ranged from 0.2 mg/L to 9.2 mg/L. The longest period of hypoxic conditions (1 day, 9 hours and 31 minutes) occurred at the bottom depth between the morning of July 29th and the morning of July 30th. During this period, bottom DO averaged around 1.51 mg/L. Chlorophyll readings increased from last week, averaging 33.5 µg/L at the surface and 22.6 µg/L at the bottom. Maximum chlorophyll at the surface reached 347.5 µg/L on the morning of August 4th. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

Sondes were swapped this week on the morning of July 30th. Overall, water quality was good at Bullock Reach this week. Salinity averaged 26.5 ppt, 28.3 ppt, and 30.1 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 15.7 – 28.3 ppt, mid salinity ranged 26.6 – 29.7 ppt, and bottom salinity ranged 28.4 – 31.3 ppt. Surface temperature averaged 24.7°C and ranged from 22.5°C to 27.7°C. Mid temperatures averaged 23.9°C and ranged from 21.8°C to 26.7°C. Bottom temperatures averaged 22.5°C and ranged from 20.8°C to 24.7°C.

DO at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface and mid depths throughout the week. Bottom DO sporadically dropped below the hypoxia threshold this week. Surface DO averaged 8.2 mg/L and ranged 4.7 – 14.4 mg/L. In the mid waters, DO averaged 5.8 mg/L and ranged 3.0 – 7.8 mg/L. At the bottom, DO averaged 3.7 mg/L and ranged 2.4 – 6.7 mg/L. The longest period of hypoxic conditions (3 hours and 30 minutes) occurred at the bottom depth during July 30th. During this period, bottom DO averaged around 2.76 mg/L. Chlorophyll readings ranged from low to elevated, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 21.8 µg/L at the surface, 17.5 µg/L at mid-depth, and 4.9 µg/L at the bottom. The maximum surface chlorophyll was 49.7 µg/L on the morning of August 2nd.

June 17, 2024

The Data Stream had an eventful day while out in the upper bay conducting routine bay bacteria monitoring activities. A 12-foot Jon Boat appeared to be in distress, as the two youths onboard could not get their motor started. The wind and the current were pushing the boat towards a concrete hurricane barrier. The Data Stream crew quickly rendered assistance and towed the youths to safety, and brought them to where they launched at the Gano Park Boat Ramp.