August 6-12, 2023

Surface chlorophyll data were collected on August 9, 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 Northern Providence River Channel, Edgewood Shoals, and Pawtuxet River Area and as fair in all other areas. Overall, chlorophyll ranged from 1.21 to 16.01 µg/L with an average of 5.34 µg/L. The chlorophyll concentrations from this date are presented in the map below using Inverse Distance Weighting (IDW) interpolation.

*Due to file error the lowest portion of the boat path for this survey is not displayed.

August 6-12, 2023

Phytoplankton samples were collected on August 9, 2023 at Bullock’s Reach and analyzed in the laboratory shortly after collection. Sonde data revealed the surface water temperature was 23.4°C, salinity was 24.1 psu, and chlorophyll a was 7.2 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. Lots of activity was present in the sample and comb jellies were detected. 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 89,000 cells per Liter. The micro flagellates were found at 70,000 cells/L. The most predominant phytoplankton genus was Dinophysis spp.at 4,000 cells/L. Other representative genera include Scripsiella spp., Guinardia spp., Eutreptiella spp., and Polykrikos spp., the featured plankton taxon in the 200x phase contrast micrograph below. 

Week of October 15 – 21, 2023

​Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on October 18, 2023 using a Seabird Electronics profiler. In the five days leading up to the survey, trace amounts of precipitation were recorded at T.F. Green. Most sites were weakly to moderately stratified this week, with  the exception of Phillipsdale Landing, which was strongly stratified.

Dissolved oxygen (DO) conditions were not observed to be below the hypoxia threshold (2.9 mg/L) at any site profiled this week. The highest fluorescence readings for the week were measured around 1 meter below the surface at India Point Park.

Week of October 8 – 14, 2023

​Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on October 11, 2023 using a Seabird Electronics profiler. In the five days leading up to the survey, 0.36 inches of precipitation were recorded at T.F. Green. All sites were strongly stratified this week.

Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the lower portion of the water column at the Edgewood Yacht Club site. The highest fluorescence readings for the week were measured around 2 meters below the surface at Conimicut Point.

Week of October 1 – 7, 2023

​Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on October 4, 2023 using a Seabird Electronics profiler. In the five days leading up to the survey, 1.27 inches of precipitation were recorded at T.F. Green. All sites were strongly or moderately stratified this week, other than Pomham Rocks, which was weakly stratified.

Dissolved oxygen (DO) conditions were not observed to be below the hypoxia threshold (2.9 mg/L) at any site profiled this week. The highest fluorescence readings for the week were measured around 2 meters below the surface at the Bullock Reach Buoy.​

Week of September 24 – 30, 2023

​​Water column profiles were conducted at six locations in the Providence and Seekonk River estuaries on September 27, 2023 using a Seabird Electronics profiler. In the five days leading up to the survey, 2.77 inches of precipitation were recorded at T.F. Green. All sites were strongly or moderately stratified this week.

Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the lower portion of the water column at the India Point Park site, and in the lower and middle portions of the water column at Point Street Bridge. The highest fluorescence readings for the week were measured around 3 meters below the surface at the Bullock Reach Buoy.

Week of September 17 – 23, 2023

​Water column profile data was collected at seven sites on September 20, 2023. However, due to an equipment deployment issue, only the data from the Phillipsdale Landing site was usable. In the five days leading up to the survey, 1.55 inches of precipitation were recorded at T.F. Green. 

At the Phillipsdale Landing, the water column here was strongly stratified. Dissolved oxygen (DO) conditions were not observed below the hypoxia threshold (2.9 mg/L), but approached this threshold near the very bottom of the water column. Fluorescence readings at this site were relatively low, but reached a maximum value approximately 2 meters below the surface.

Week of September 10 – September 16, 2023

​Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on September 14, 2023 using a Seabird Electronics profiler. In the five days leading up to the survey, 1.23 inches of precipitation were recorded at T.F. Green. All sites were strongly stratified this week.

Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the lower portion of the water column at the Bullock Reach Buoy and Phillipsdale Landing sites, in the lower and middle portions of the water column at Conimicut Point and Point Street Bridge, and in all portions of the water column (upper, middle, and lower) at India Point Park, Pomham Rocks, and Edgewood Yacht Club. The highest fluorescence readings for the week were measured around 1.5 meters below the surface at Edgewood Yacht Club.

Week of August 6 – 12, 2023

​Nutrient samples were collected from seven river stations and seven bay stations on August 9th, 2023. All bay stations were sampled at the surface and bottom. In the five days prior to sampling, there were 0.48 inches of rainfall 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 = 1,390 ppb, TDN = 1,520 ppb, and DIN = 1244.2 ppb). The lowest TN and TDN were observed at Moshassuck River @ Footbridge at Mill Street (TN = 741.5 ppb, TDN= 680.5 ppb, average of duplicates), while the lowest DIN was at Blackstone River @ Bikepath Bridge (DIN = 484.7 ppb).

Among the bay stations sampled, the highest surface TN, TDN, and DIN concentrations were observed at Phillipsdale Landing (TN = 1,050 ppb, TDN = 919 ppb, DIN = 561 ppb). The lowest surface TN, TDN, and DIN concentrations were observed at Conimicut Point (TN = 738 ppb, TDN = 360 ppb, DIN = 143.2 ppb). Chlorophyll a concentrations at the surface bay stations averaged 4.16 μg/L overall with a maximum at the Bullock Reach Buoy (6.94 μg/L, average of duplicates).

Week of September 3 – September 9, 2023

​Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on September 6, 2023 using a Seabird Electronics profiler. In the five days leading up to the survey, no precipitation was recorded at T.F. Green. Most sites were moderately to weakly stratified this week.

Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the lower portion of the water column at the Pomham Rocks, India Point Park, and Phillipsdale Landing sites. The highest fluorescence readings for the week were measured around 1.5 meters below the surface at Edgewood Yacht Club.

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