March 19, 2025

Nutrient samples were collected from seven river stations and eight bay stations on March 19th. 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 5th. 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.

June 11, 2025

Phytoplankton samples were collected on June 11, 2025 at Bullock’s Reach and analyzed in the laboratory shortly after collection.

The water temperature was 18.0 °C, the salinity was 21.28 psu, and the chlorophyll a was 4.24 ug/L.

The qualitative tow net sample had a moderate filtration time. The filtrate had a medium brown/green coloration.

The analysis of the quantitative whole water sample revealed a total of 5,517,000 cells/L. The microflagellates were found at 112,000 cells/L. The most predominant phytoplankton genera were Guinardia spp. at 1,652,000 cells/L, Chaetoceros spp. at 1,448,000 cells/L, and Leptocylindrus spp. at 1,044,000 cells/L.

200x phase contrast micrograph of phytoplankton

June 25, 2025

Surface chlorophyll data were collected on June 25, 2025, while the R/V Monitor was underway collecting nutrient samples in the Providence and Seekonk River estuary. The average chlorophyll concentrations were categorized as fair in the Seekonk River, and as good in all other areas. The average chlorophyll concentrations were categorized as good in all areas surveyed. Overall, chlorophyll ranged from 0.39 µg/L to 17.96 µg/L with an average of 2.01 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation. 

June 11, 2025

Surface chlorophyll data were collected on June 11, 2025, 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 the Seekonk River and Pawtuxet River, and as fair in all other areas. Overall, chlorophyll ranged from 2.85 µg/L to 28.47 µg/L with an average of 19.66 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

June 4, 2025

Surface chlorophyll data were collected on June 4, 2025, 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 the Seekonk River, and as fair in all other areas. Overall, chlorophyll ranged from 1.10 µg/L to 16.10 µg/L with an average of 7.24 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation. 

May 28, 2025

Surface chlorophyll data were collected on May 28, 2025, while the R/V Monitor was underway collecting nutrient samples in the Providence and Seekonk River estuary. The average chlorophyll concentrations were categorized as fair in the Southern Providence River, and as good in all other areas. Overall, chlorophyll ranged from 1.35 µg/L to 13.49 µg/L with an average of 5.43 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation. 

June 25, 2025

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on June 25, 2025. In the five days prior to the survey, 0.01 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.3 meters. The lowest clarity this week (1.3 meters) was measured at Phillipsdale Landing, while the greatest clarity (2.7 meters) was measured at India Point Park and Pomham Rocks. There was no clear north-to-south gradient in water clarity among the sites this week. Overall, water clarity at most locations remained relatively consistent compared to previous measurements (data collected June 11, 2025).

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