Historical News
Surface Mapping
Data
were collected on September 2, 2020 while the R/V Monitor was underway
collecting bacteria samples and performing vertical profiles in the Providence
and Seekonk River estuaries. The chlorophyll concentrations were variable from
poor to good in the areas surveyed with evidence of a north-south gradient. From
north to south, average chlorophyll concentrations were as follows: Seekonk
River (35.16 µg/L), Upper Providence River (34.65 µg/L), Edgewood Shoals area (21.17
µg/L), Pawtuxet River area (22.79 µg/L), and Lower Providence River area (13.87
µg/L). Overall, chlorophyll ranged between 3.10 µg/L and 187.50 µg/L with an
overall average of 27.18 µg/L. The chlorophyll data from this date are
presented in the map below:
Water Column Profiles
The NBC's Seabird profiling instrument was sent to the manufacturer for routine servicing over the winter; due to the COVID-19 pandemic, the return of the instrument has been greatly delayed. In the absence of this instrument, the NBC Environmental Monitoring Department has used a YSI EXO sonde to collect data on surface and bottom conditions at eight typical Seabird profiling sites on August 19. Settings on this instrument were not optimized for measurements of a true profile, rather, the goal was to obtain stable estimates of conditions at the surface and bottom only. These data are summarized here, and raw data are available upon request. In the five days prior to sampling, 0.5 inches of rainfall occurred. Stratification was present at most sites.
Salinities were highest at Conimicut Point, measuring 31.4 ppt at the surface and 32.2 ppt at the bottom. The lowest surface salinity (15.4 ppt) occurred at Pawtuxet Cove, while the lowest bottom salinity (27.7 ppt) was measured at India Point Park. Water temperatures were warmest at Point Street Bridge, ranging from 27.2°C at the surface to 27.0°C at the bottom. Surface waters were coolest at Bullock Reach, averaging 22.8°C, while bottom waters were coolest at Conimicut Point, averaging 21.6°C.
Dissolved oxygen (DO) concentrations were good this week; bottom waters at all sites remained above the hypoxia threshold (2.9 mg/L). Water column dissolved oxygen was lowest at Point Street Bridge, ranging from 4.7 mg/L in surface waters to 3.8 mg/L in bottom waters. The highest average surface DO (7.6 mg/L) was observed at Conimicut Point, while DO in bottom waters was greatest at Pawtuxet Cove (6.2 mg/L). Average surface chlorophyll ranged from 5.0 ug/L at Pomham Rocks to 24.5 ug/L at Bullock Reach; the maximum value recorded at Bullock Reach was 39.8 ug/L.
Water Column Clarity
Water clarity was measured at eight locations in the Providence and Seekonk Rivers on August 19, 2020. The weather leading up to the survey date was moderately wet, with 0.5 inches of rainfall recorded over the three days prior to sampling. Secchi depth increased at all sites compared to the previous survey, with an overall average of 1.95 m compared to 0.94 the week before. The greatest clarity, and greatest increase from the prior week was observed at Conimicut Point, where the Secchi depth of 3.70 m was substantially higher than 1.47 m measured on August 13. The lowest clarity overall was measured at Phillipsdale Landing at 1.10 m. A general gradient in increasing clarity from north to south was observed among sites this week.
Water Column Clarity
Water clarity was measured at eight locations in the Providence and Seekonk Rivers on August 13, 2020. The weather leading up to the survey date was dry, with just 0.01 inches of rainfall recorded the day before sampling and no rainfall over the four days prior to that. Average Secchi depth decreased by 0.46 m compared to the previous week, from 1.40 m to 0.94 m. All individual sites that were surveyed the previous week exhibited a decrease in clarity, the greatest of which was observed at Bullock Reach; clarity at this site declined from 1.90 m on August 5 to 0.77 m on August 13. The lowest clarity overall was measured at Edgewood Yacht Club at 0.30 m; the greatest clarity was observed at Conimicut Point at 1.47 m. There was no apparent gradient in clarity from north to south this week.
Water Column Clarity
Water clarity was measured at seven locations in the Providence and Seekonk Rivers on August 5, 2020. A total of 0.25 inches of precipitation was recorded over five days prior to the survey, with the majority (0.19 inches) recorded on August 4. Average Secchi depth decreased by 0.30 m since the last survey (July 22), from 1.70 m to 1.40 m. The greatest decrease in water clarity was observed at Phillipsdale Landing, which decreased from 1.97 m to 0.70 m; this was the lowest clarity measured this week. Water clarity also exhibited decreases at Point St. Bridge, Edgewood Yacht Club, and Pomham Rocks. Water clarity increased at Bullock Reach (+0.27 m) and Conimicut Point (+0.20 m); Secchi depth was greatest at these two sites, at 1.90 m. A gradient of increasing water clarity among sites from north to south was apparent.
