News – Page 6 – Narrabay

July 2, 2025

Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on July 2, 2025. In the five days prior to the survey, 0.02 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.2 meters. The lowest clarity this week (1.4 meters) was measured at Phillipsdale Landing, while the greatest clarity (2.9 meters) was measured at Conimicut Point. There was a general north-to-south trend of increasing water clarity among the sites this week. Overall, water clarity remained approximately the same from the previous measurements (data collected June 25, 2025).

May 28, 2025

Nutrient samples were collected from fourteen river stations and eight bay stations on May 28^th. All bay stations were sampled at the surface and one station (Edgewood Shoal) was sampled at the bottom. In the five days prior to sampling, 0.06 inches of precipitation were recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed Ten Mile River @ Central Ave. (TN = 1,050 ppb, TDN = 1,100 ppb, DIN = 757). The lowest TN, and TDN were observed at Moshassuck River @ Higginson Ave. (TN = 458 ppb, TDN = 552 ppb). The lowest DIN was observed at Coles River @ Milford Rd. (DIN = 116 ppb).

Among the bay stations sampled, the highest surface total nitrogen (TN) was observed at Phillipsdale Landing (TN = 870 ppb). The highest total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Pawtuxet Cove (TDN = 771 ppb, DIN = 568 ppb). The lowest surface TN was observed at the Bullock Reach Buoy (TN = 584). The lowest surface TDN and DIN concentrations were observed at Conimicut Point (TDN = 214 ppb, DIN = 72 ppb).

The next scheduled sampling date is June 11, 2025.

May 14, 2025

Nutrient samples were collected from seven river stations and seven bay stations on May 14^th. All bay stations were sampled at the surface and the bottom. In the five days prior to sampling, 0.29 inches of precipitation were recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN) was observed at Blackstone River @ Bikepath Bridge. (TN = 823 ppb). The highest total dissolved nitrogen (TDN) was observed at Blackstone River @ Slater Mill (TDN = 993 ppb). The highest dissolved inorganic nitrogen was observed at Pawtuxet River @ Broad St. (DIN = 520 ppb). The lowest TN, and DIN were observed at the Moshassuck River @ Footbridge at Mill St. (TN = 636 ppb, DIN = 683 ppb). The lowest TDN was observed at Blackstone River @ Stateline (TDN 428 ppb).

Among the bay stations sampled, the highest surface total nitrogen (TN) was observed at India Point Park (TN = 857 ppb). The highest total dissolved nitrogen (TDN) was observed at Phillipsdale Landing (TDN = 736 ppb). The highest dissolved inorganic nitrogen (DIN) was observed at Pawtuxet Cove (DIN = 453 ppb). The lowest surface TN, TDN and DIN concentrations were observed at Conimicut Point (TN = 645 ppb, TDN = 359 ppb, DIN = 183 ppb).

The next scheduled sampling date is May 28, 2025.

April 30, 2025

Nutrient samples were collected from seven river stations April 30^th. In the five days prior to sampling, 0.76 inches of precipitation were recorded at T.F. Green.

The highest total nitrogen (TN), total dissolved nitrogen (TDN) and dissolved inorganic nitrogen (DIN) concentrations were observed at Pawtuxet River @ Broad St. (TN = 1,120 ppb, TDN = 1,100 ppb, DIN = 875 ppb). The lowest TN, TDN and DIN concentrations were observed at Moshassuck River @ Footbridge at Mill St. (TN =670 ppb, TDN = 722 ppb, DIN = 427 ppb).

The next scheduled sampling date is May 14, 2025.

April 16-17, 2025

Nutrient samples were collected from seven river stations on April 16^th and seven bay stations 17^th. All bay stations were sampled at the surface and bottom except for one station (India Point Park) which was only sampled at the surface. In the five days prior to sampling, 0.80 inches of precipitation were recorded at T.F. Green. Due to a laboratory issue, some ammonia and dissolved inorganic nitrogen (DIN) results for the bay and river samples are not available. The DIN for both the bay and river stations will be based on the results available.

Among the river stations sampled, the highest total nitrogen (TN) was observed at Blackstone River @ Slater Mill (TN = 953 ppb). The highest total dissolved nitrogen (TDN) and dissolved inorganic nitrogen (DIN) was observed at Pawtuxet River @ Broad St. (TDN = 930 ppb, DIN = 673 ppb). The lowest TN and TDN were observed at Moshassuck River @ Footbridge at Mill St. (TN = 569 ppb, TDN = 517 ppb). The lowest DIN was observed at Blackstone River @ Bikepath Bridge. (DIN = 614 ppb).

Among the bay stations sampled, the highest surface total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Phillipsdale Landing (TN = 1,250 ppb, TDN = 975 ppb, DIN = 801 ppb). The lowest surface TN and DIN concentrations were observed at Conimicut Point (TN = 504 ppb, DIN = 79 ppb). The lowest surface TDN was observed at the Bullock Reach Buoy (TDN = 178 ppb).

The next scheduled sampling date is April 30, 2025.

April 2, 2025

Nutrient samples were collected from twelve river stations on April 2^nd. In the five days prior to sampling, 0.25 inches of precipitation were recorded at T.F. Green.

The highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Ten Mile River @ Central Ave. (TN = 2,040 ppb, TDN = 2,020 ppb, DIN = 1,731). The lowest TN, and TDN concentrations were observed at Moshassuck River @ Footbridge at Mill St. (TN = 546 ppb, TDN = 543 ppb). The lowest DIN concentration was observed at Coles River @ Milford Rd. (DIN = 160 ppb).

The next scheduled sampling date is April 16, 2025.

March 19, 2025

Nutrient samples were collected from seven river stations and eight bay stations on March 19^th. All bay stations were sampled at the surface and the bottom. In the five days prior to sampling, 2.21 inches of precipitation were recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN) and dissolved inorganic nitrogen (DIN) were observed at Blackstone River @ Slater Mill (TN = 1,220 ppb, TDN = 1,160, DIN = 810). The lowest TN, and TDN concentrations were observed on the Woonasquatucket River @ Manton Ave. Bridge (TN = 624 ppb, TDN = 617 ppb). The lowest DIN was observed at Moshassuck River @ Footbridge at Mill St. (DIN = 407 ppb).

Among the bay stations sampled, the highest surface total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Phillipsdale Landing (TN = 1,450 ppb, TDN = 1,290 ppb, DIN = 889 ppb). The lowest surface TN was observed at Pomham Rocks (TN = 766 ppb). The lowest surface TDN and DIN concentrations were observed at Conimicut Point Surface (TDN = 475 ppb, DIN = 223 ppb).

The next scheduled sampling date is April 2, 2025.

March 5, 2025

Nutrient samples were collected from six river stations on March 5^th. In the five days prior to sampling, there was no precipitation recorded at T.F. Green.

The highest total nitrogen (TN), total dissolved nitrogen (TDN) and dissolved inorganic nitrogen (DIN) concentrations were observed at Pawtuxet River @ Broad St. (TN = 1,590 ppb, TDN = 1,770 ppb, DIN = 1,533 ppb). The lowest TN, TDN, and DIN concentrations were observed on the Moshassuck River @ Footbridge at Mill St. (TN =558 ppb, TDN = 592 ppb, DIN = 441 ppb).

The next scheduled sampling date is March 19, 2025.

June 25, 2025

Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on June 25, 2025 using a Seabird Electronics profiler. In the five days leading up to the survey, 0.01 inches of precipitation were recorded at T.F. Green. Water column stratification varied between the sites this week from weakly stratified at Pawtuxet Cove to strongly stratified at Conimicut Point, Pomham Rocks, and Phillipsdale Landing.

Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the lower portion of the water column at India Point Park and Phillipsdale Landing. The highest fluorescence readings for the week were measured around 1 meter below the surface at Phillipsdale Landing.

June 25, 2025

Phytoplankton samples were collected on June 25, 2025 at Bullock’s Reach and analyzed in the laboratory shortly after collection.

The water temperature was 24.98 °C, the salinity was 24.10 psu, and the chlorophyll a was 8.14 ug/L.

The qualitative tow net sample had a long filtration time. The filtrate contained jellyfish and had a golden brown coloration.

The analysis of the quantitative whole water sample revealed a total of 1,501,000 cells/L. The microflagellates were found at 330,000 cells/L. The most predominant phytoplankton genera were Cerataulina spp. at 437,000 cells/L, Skeletonema spp. at 287,000 cells/L, and Heterocapsa spp. at 147,000 cells/L.

200x phase contrast micrograph of *Akashiwo sanguinea*

Akashiwo sanguinea is a planktonic dinoflagellate which lives as a single cell and uses one flagellum for locomotion. These dinoflagellates are mixotrophic, which means they can use different sources for energy and carbon uptake. They are photosynthetic, containing a large number of chloroplasts radiating from the center of the cell, and also prey on various types of smaller organisms.