News – Page 38 – Narrabay

March 6, 2024

Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on March 6, 2024 using a Seabird Electronics profiler. In the five days leading up to the survey, 2.30 inches of precipitation were recorded at T.F. Green. Most sites were strongly stratified this week, with the exception of Phillipsdale Landing, which was dominated by freshwater, showing the impact of over 2 inches over rain that fell in the days before the profiles were recorded.

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 1.5 meters below the surface at Conimicut Point.

Week of December 10 – 16, 2023

Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on December 13, 2023 using a Seabird Electronics profiler. In the five days leading up to the survey, 2.29 inches of precipitation were recorded at T.F. Green. Most sites were strongly stratified this week, with the exception of Pawtuxet Cove, which was dominated by freshwater, showing the impact of the major rain storm this week.

Week of November 26 – December 2, 2023

Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on November 30, 2023 using a Seabird Electronics profiler. In the five days leading up to the survey, 0.69 inches of precipitation were recorded at T.F. Green. Most sites were weakly or moderately stratified this week, with the exception of Pawtuxet Cove, which was strongly stratified.

Week of November 12 – 18, 2023

Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on November 15, 2023 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. Stratification ranged from well-mixed at sites like Bullock Reach Buoy to moderately stratified at sites including Phillipsdale Landing and Pomham Rocks.

Week of October 29 – November 5, 2023

Water column profiles were conducted at seven locations in the Providence and Seekonk River estuaries on November 1, 2023 using a Seabird Electronics profiler. In the five days leading up to the survey, 1.11 inches of precipitation were recorded at T.F. Green. Most sites were moderately stratified this week, with the exception of Phillipsdale Landing, and Pawtuxet Cove, which were strongly stratified.

Week of October 22 – 28, 2023

Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on October 25, 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. Stratification varied between the profiled sites this week, from weak stratification at Pomham Rocks and Point Street Bridge, to strong stratification at India Point Park, Phillipsdale Landing, and Pawtuxet Cove.

August 6-12, 2023

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on August 9. Rainfall totaling 0.48 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 1.8 meters, compared to 2.3 meters on the previous survey (August 2). The lowest clarity this week (1.2 meters) was measured at Phillipsdale Landing, while the greatest clarity (2.1 meters) was measured at Pomham Rocks. There was no clear north-to-south gradient in water clarity among the sites this week.

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.