News – Page 18 – Narrabay

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.

July 10, 2024

Surface chlorophyll data were collected on July 10, 2024 while the R/V Monitor was underway collecting nutrient samples in the Providence and Seekonk River estuaries. The average chlorophyll concentrations were categorized as poor in the Seekonk River and Northern Providence River Channel and as good in all other areas. Overall, chlorophyll ranged 0.81 to 82.48 µg/L with an average of 19.85 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

July 3, 2024

Surface chlorophyll data were collected on July 3, 2024 while the R/V Monitor was underway collecting bacteria samples in the Providence and Seekonk River estuaries. The average chlorophyll concentrations were categorized as poor in the Lower Providence River Area and as fair in all other areas. Overall, chlorophyll ranged from 2.27 to 52.87 µg/L with an average of 16.49 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

June 17, 2024

Surface chlorophyll data were collected on June 17, 2024 while the R/V Monitor was underway collecting bacteria samples in the Providence and Seekonk River estuaries. The average chlorophyll concentrations were categorized as poor in the Seekonk River and as fair in all other areas. Overall, chlorophyll ranged from 0.0 to 72.05 µg/L with an average of 13.74 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

July 24, 2024

Nutrient samples were collected from eleven river stations and eight bay stations on July 24th. 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 0.06 inches 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) concentrations were observed at Ten Mile River @ Central Ave (TN = 1,940 ppb, TDN = 1,800 ppb, DIN = 1,650 ppb). The lowest TN was observed at Runnins River @ River Rd (742 ppb), while the lowest TDN and DIN were observed at Palmer River @ Rt 6 (TDN = 387 ppb, DIN = 78 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 = 1,300 ppb, TDN = 1,100 ppb, DIN = 840 ppb). The lowest surface TN was at India Point Park (600 ppb, average of duplicates), while the lowest surface TDN and DIN concentrations were observed at Conimicut Point (TDN = 280 ppb, DIN = 30 ppb).

The next scheduled sampling date is August 7, 2024.

May 29, 2024

Phytoplankton samples were collected on May 29, 2024 at Bullock Reach and analyzed in the laboratory shortly after collection.

Sonde data revealed the surface water temperature was 20.1°C, salinity was 15.49 psu, and chlorophyll a was 12.1 ug/L.

The qualitative tow net sample had a moderate filtration time, and the filtrate was a dark tan/brown color and had particulate matter.

The analysis of the quantitative whole water sample revealed a total of 7,565,000 cells per Liter. The most predominant phytoplankton genus was Skeletonema spp. at 7,276,000 cells/L. Other representative genera include Chaetoceros spp. and Leptocylindrus spp. Chaetoceros spp. (see 200x phase contrast image below) is a genus of diatoms found in Narragansett Bay and is one of the most common and most diverse genera of marine planktonic diatoms with over 200 accepted species. Due to its high growth rates, research has been conducted into potential uses of Chaetoceros in biotechnology.

July 10, 2024

Nutrient samples were collected from seven river stations and seven bay stations on July 10th. All bay stations were sampled at the surface and bottom. 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), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) concentrations were observed at Pawtuxet River @ Broad St (TN = 1,350 ppb, TDN = 1,340 ppb, DIN = 995 ppb). The lowest TN, TDN, and DIN were observed at Blackstone River @ Slater Mill (TN = 873 ppb, TDN = 794 ppb, DIN = 568 ppb).

Among the bay stations sampled, the highest surface total nitrogen (TN) concentration was observed at Phillipsdale Landing (1,240 ppb); the highest total dissolved nitrogen (TDN) and dissolved inorganic nitrogen (DIN) were at Pawtuxet Cove (TDN = 1,000 ppb, DIN = 718 ppb, average of duplicates). The lowest surface TN and TDN were at Conimicut Point (TN = 511 ppb, TDN = 261 ppb), while the lowest surface DIN concentrations were observed at Edgewood Yacht Club, Pomham Rocks, and India Point Park (13 ppb).

The next scheduled sampling date is July 24, 2024.

June 26, 2024

Nutrient samples were collected from twelve river stations on June 26th. In the five days prior to sampling, there were 1.44 inches 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) concentrations were observed at Ten Mile River @ Central Ave. (TN = 1,335 ppb, TDN = 1,375 ppb, DIN = 1,109 ppb, all averaged with duplicates). The lowest TN and TDN were observed at Runnins River @ River Road (TN = 588 ppb, TDN = 585 ppb), while the lowest DIN was at Palmer River @ Rt. 6. (DIN = 241 ppb).

The next scheduled sampling date is July 10, 2024.

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.

June 12, 2024

Surface chlorophyll data were collected on June 12, 2024 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 Pawtuxet River, poor in the Northern Providence River Channel, and as fair in all other areas. Overall, chlorophyll ranged from 1.48 to 44.81 µg/L with an average of 14.44 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.