Historical News
Water Column Profiles
Phillipsdale Landing had the lowest water column salinities, with values ranging from 7.0 psu at the surface to 30.5 psu at the bottom. The greatest surface salinity (23.9 psu) was measured at Edgewood Shoal, while the greatest bottom salinity (30.5 psu) occurred at Conimicut Point. Coldest temperatures occurred at India Point Park, where temperatures ranged from 10.3°C in bottom waters to 14.1°C at the surface. Warmest surface temperature was measured at Phillipsdale Landing (18.7°C), while warmest bottom waters (13.6°C) occurred at Pawtuxet Cove.
Dissolved oxygen (DO) ranged from 6.9 mg/L at a depth of 4 meters at Edgewood Shoal to 12.9 mg/L in surface waters at Pawtuxet Cove. Hypoxic conditions (DO < 2.9 mg/L) were not observed at any of the sites during this survey. Generally, fluorescence was low, with some slight evidence of phytoplankton activity in surface waters at Conimicut Point and Phillipsdale Landing. Please note that due to a quality control issue, numerical fluorescence data are not posted at this time.
Fixed Site Network
Phillipsdale Landing
Phillipsdale Landing sondes were changed out for routine maintenance during mid-day on May 11. Overall, water quality at this site was good this week. A total of 1.02 inches of rainfall was recorded at TF Green, with a majority (0.85 inches) occurring on May 10. Following the rain event on May 10, Blackstone River flows decreased leading to a slight decrease in surface and bottom salinity. Salinity at the surface averaged 6.3 ppt and ranged from 1.9 ppt to 13.9 ppt, while bottom salinity averaged 19.6 ppt and ranged from 4.7 ppt to 29.1 ppt. Surface water temperatures this week were warmer than the previous week, averaging 14.9°C and ranging from 12.1°C to 18.8°C. Bottom water temperatures averaged 12.5°C and ranged from 10.4°C to 16.3°C.
Dissolved oxygen (DO) remained well above the hypoxia threshold (2.9 mg/L) this week. Surface DO averaged 9.4 mg/L, with a minimum of 8.1 mg/L, while bottom DO averaged 7.5 mg/L, with a minimum of 5.6 mg/L. In general, chlorophyll concentrations continue to remain low, averaging 2.6 ug/L at the surface and 4.1 ug/L at the bottom. Maximum surface concentrations reached 10.3 ug/L on May 9, suggesting a slight increase in phytoplankton activity earlier in the week and decreasing through the week. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and dissolved oxygen at this location; chlorophyll readings could also be impacted by suspended matter/particulates and macroalgae.
Bullock Reach
Bullock Reach sondes will be deployed the first week of June.
Fixed Site Network
Phillipsdale Landing
Water quality at Phillipsdale was good this week. A total of 1.10 inches of rainfall was recorded at TF Green, with a majority (0.77 inches) occurring on May 4. Blackstone River flows increased following the rain event on May 4, leading to a general decrease in salinity concentrations compared to the previous week. Salinity at the surface averaged 6.8 ppt and ranged from 2.3 ppt to 14.5 ppt. Bottom salinity averaged 19.9 ppt and ranged form 6.0 ppt to 29.2 ppt. Surface water temperatures in general were warmer than the previous week, averaging 14.1°C and ranging from 12.3°C to 16.6°C. Bottom water temperatures averaged 11.8°C and ranged from 9.8°C to 14.4°C.
Dissolved oxygen (DO) remained well above the hypoxia threshold (2.9 mg/L) this week. Surface DO averaged 9.5 mg/L, with a minimum of 8.1 mg/L, while bottom DO averaged 7.1 mg/L, with a minimum of 5.0 mg/L. Chlorophyll concentrations in general continue to remain low, averaging 5.0 ug/L at the surface and 21.3 ug/L at the bottom. Maximum surface concentrations reached 26.3 ug/L on May 3, suggesting increased phytoplankton activity earlier in the week and decreasing through the week. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and dissolved oxygen at this location; chlorophyll readings could also be impacted by suspended matter/particulates and macroalgae.
Bullock Reach
Bullock Reach sondes will be deployed the first week of June.
Phytoplankton Sampling
Phytoplankton samples were collected on May 19, 2021 at Bullock Reach and analyzed in the laboratory shortly after collection. It was a sunny and gorgeous day on Narragansett Bay. Sondes data revealed the surface water temperature was 16.2°C, salinity was 22.0 psu, and chlorophyll a was 2.6 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a thick golden brown color and had a quick filter time. The tow net sample was analyzed qualitatively for microorganisms using 100x 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 5,580,000 cells per Liter. The flagellates were found at 69,000 cells/L. The most predominant phytoplankton genus was Skeletonema spp. at 4,536,000 cells/L. Many were found in chains of 6-8 cells. Other representative genera include Chaetoceros spp., Thalassiosira spp., and pennate diatoms.
100x phase contrast image of the tow net phytoplankton.
Water Column Profiles
Lowest salinities were measured at Phillipsdale Landing, with values ranging from 4.8 psu at the surface to 27.8 psu at the bottom. Highest surface salinity, 25.5 psu, was measured at Bullock Reach. Greatest bottom salinity (30.4 psu) was measured at Conimicut Point. Surface water temperatures ranged from 10.9°C at India Point Park to 13.6°C at Phillipsdale Landing. Bottom water temperatures ranged from 9.5°C at India Point Park to 10.6°C at Edgewood Yacht Club.
Dissolved oxygen (DO) ranged from 8.2 mg/L in bottom waters at Phillipsdale Landing to 10.3 mg/L in surface waters at Bullock Reach and Conimicut Point. Hypoxic conditions (e.g., DO concentrations < 2.9 mg/L) were not observed at any sites. Generally, fluorescence readings were low among all sites with no strong evidence of phytoplankton blooms. Please note that due to a quality control issue, numerical fluorescence data are not posted at this time.
