Week of September 05 – 11, 2021
Nutrients Sampling
Nutrient samples were collected from seven local river stations and three bay stations on September 8, 2021; the Bay stations were all sampled at the surface and bottom. Please note that due to mechanical issues with the NBC research vessel, R/V Monitor, there was limited Bay nutrient sampling this week. Weather conditions leading up to the sampling day were mostly dry, with 0.02 inches of recorded rainfall in the five days prior to sampling.
Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were all observed at Moshassuck River at Mill Street. At this site, the average of two duplicates for TN, TDN, and DIN concentrations were 930 ppb, 879.5 ppb, and 764.1 ppb, respectively. The lowest TN (644 ppb) and DIN (376.7 ppb) were observed at Blackstone River at Slater Mill, while the lowest TDN( 639 ppb) was observed Blackstone River at Stateline.
Among the Bay stations sampled, the highest surface TN (778 ppb) and DIN (428.1 ppb) were observed at Phillipsdale Landing, while the highest TDN (812.5 ppb; average of two duplicates) was observed at Edgewood Shoal. The lowest surface TN (699 ppb) and TDN (662 ppb) were observed at Edgewood Yacht Club, while the lowest DIN (311.5 ppb; average of two duplicates) was observed at Edgewood Shoal. Chlorophyll a concentrations at the Bay sites decreased since the previous sampling event, averaging 2.54 ug/L across all sites. The maximum result of 3.09 ug/L occurred at Edgewood Shoal (average of two duplicates).
Results from nutrient sampling on September 14 are pending analysis. The next scheduled sample date is September 22.
Week of June 27 – July 03, 2021
Water Column Profiles
Water column profiles were at six locations in the Providence River using a Seabird profiling instrument on July 30, 2021. Conditions leading up to sampling were dry with no rainfall recorded at T.F. Green. Evidence of density stratification was observed at two locations: Conimicut Point and Edgewood Yacht Club.
Surface salinities among all sites ranged from 19.3 psu at India Point Park to 24.1 psu at Conimicut Point. Bottom salinities ranged from 23.6 psu at Pawtuxet Cove. The warmest water temperatures were observed at Pawtuxet Cove, ranging from 26.2°C at the surface to 24.6°C at the bottom. The lowest surface temperatures (25.3°C) were observed at Conimicut Point, while the lowest bottom temperatures (18.9°C) were observed at India Point Park.
This week, hypoxic conditions (dissolved oxygen (DO) concentrations <2.9 mg/L) were observed in the bottom waters at India Point Park. Across all sites, DO ranged from 2.3 mg/L in bottom waters at India Point Park to 12.9 mg/L at the surface at Edgewood Yacht Club. Highest florescence occurred in the surface waters at Pomham Rocks. Please note that due to quality control issue, numerical fluorescence data are not posted at this time.
Week of September 12 - 18, 2021
Fixed Site Network
Phillipsdale Landing
Water quality at Phillipsdale Landing was fair-to-poor this week. Sondes were swapped out for routine maintenance mid-day on September 14th. Blackstone River flows remained elevated above historical median flows, though generally declined over the course of the week. Rainfall was light to moderate, just 0.8 inches on September 16th as measured at TF Green. Salinity at the surface increased compared to the week before, averaging 6.0 ppt and ranging 1.8-18.3 ppt. Bottom salinity averaged 17.8 ppt and ranged 3.3-28.3 ppt. Water temperatures averaged 21.9°C on the surface and bottom. Surface temperatures ranged from 20.0°C to 23.8°C while bottom temperatures ranged from 20.5°C to 23.4°C.
Surface dissolved oxygen (DO) averaged 6.7 mg/L, with a minimum of 2.8 mg/L. Hypoxic conditions (DO ≤ 2.9 mg/L) at the surface consisted of an isolated single reading on September 18th. Bottom DO was hypoxic approximately half of the week, coincident with high tides. The average bottom DO was 3.4 mg/L, with a minimum of 1.8 mg/L and maximum of 7.5 mg/L. Hypoxic conditions persisted for up to 10 hours at a time. Chlorophyll concentrations remained low this week, averaging 3.6 ug/L on the surface and 3.4 ug/L on the bottom, with a surface maximum of 9.7 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
Sondes were swapped out for maintenance on the morning of September 14th. The retrieved sondes had been deployed for three weeks, compared to the routine two-weeks, with the delay due to the NBC's research vessel being out of service. Water quality at Bullock Reach was fair this week. Salinity at the surface averaged 22.6 ppt and ranged from 18.3 ppt to 26.0 ppt. Salinity at the mid depth averaged 26.7 ppt and ranged from 22.9 ppt to 30.2 ppt. Salinity in bottom waters averaged 29.3 ppt and ranged from 26.1 ppt to 31.6 ppt. Temperatures were similar to the previous week, averaging 22.3°C, 21.9°C, and 21.2°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 21.3°C to 23.3°C, mid temperatures ranged from 20.7°C to 23.2°C, and bottom temperatures ranged from 20.2°C to 22.5°C.
DO concentrations were also similar to the previous week, averaging 6.9 mg/L at the surface, 5.5 mg/L at mid-depth, and 4.0 mg/L at the bottom. Waters at all depths remained above the hypoxia threshold, with minimum bottom DO measuring 3.1 mg/L. Chlorophyll concentrations averaged 18.6 ug/L at the surface and 7.9 ug/L at mid-depth. Concentrations were highest in the first half of the week, with the bloom activities from the prior week beginning to dissipate around Tuesday. The maximum chlorophyll value in surface waters was 88.2 ug/L, on September 13th.
Week of September 5 - 11, 2021
Fixed Site Network
Phillipsdale Landing
Water quality at Phillipsdale Landing was fair-to-poor this week. Blackstone River flows remained elevated above historical median flows, though generally declined over the course of the week. Rainfall was light to moderate, just 0.2 inches on September 6th and 0.5 inches on September 9th as measured at TF Green. Salinity at the surface averaged 3.4 ppt and ranged 0.5-8.1 ppt. Bottom salinity averaged 13.6 ppt and ranged 1.3-29.4 ppt. Water temperatures cooled slightly compared to the previous week, averaging 21.2°C on the surface and 21.3°C on the bottom. Temperatures ranged from 19.3°C to 22.7°C at the surface and from 19.6°C to 22.5°C at the bottom.
Surface dissolved oxygen (DO) averaged 7.7 mg/L, with a minimum of 6.3 mg/L. Bottom DO continued to dip below the hypoxia threshold (2.9 mg/L) during most high tide periods, generally decreasing over the course of the week. The average bottom DO was 4.9 mg/L, with a minimum of 1.7 mg/L and maximum of 8.8 mg/L. The longest duration of hypoxic conditions this week was on September 11th for approximately 7 hours around the mid-day high tide. Chlorophyll concentrations remained low, averaging 2.6 ug/L on the surface and 1.8 ug/L on the bottom, with a surface maximum of 8.2 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
Water quality at Bullock Reach was fair this week. Salinity at the surface averaged 21.5 ppt and ranged from 15.8 ppt to 25.2 ppt. Salinity at the mid depth averaged 26.6 ppt and ranged from 22.3 ppt to 29.9 ppt. Salinity in bottom waters averaged 29.5 ppt and ranged from 24.1 ppt to 31.7 ppt. Temperatures cooled slightly since the previous week, averaging 22.1°C, 21.9°C, and 21.3°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 20.8°C to 23.2°C, mid temperatures ranged from 21.3°C to 22.9°C, and bottom temperatures ranged from 20.7°C to 22.6°C.
DO concentrations improved this week, averaging 6.7 mg/L at the surface, 5.2 mg/L at mid-depth, and 3.7 mg/L at the bottom. Hypoxic conditions (DO ≤ 2.9 mg/L) were observed only in bottom waters and only for isolated short durations. The longest period of hypoxia this week was approximately 1 hour during the evening of September 8th. Chlorophyll concentrations averaged 13.4 ug/L at the surface and 10.5 ug/L at mid-depth. Concentrations increased in the latter half of the week, suggestive of phytoplankton bloom activity. The maximum chlorophyll value in surface waters was 64.8 ug/L, on September 11th.
Week of August 29 – September 04, 2021
Fixed Site Network
Phillipsdale Landing
Water quality at Phillipsdale Landing was fair-to-poor this week. Sondes were swapped for routine maintenance during the morning of August 31st. Rainfall this week totaled 3.95 inches at TF Green, with a majority of the rainfall (3.89 inches) occurring in the first two days of September. Impacted by the heavy rainfall at the end of the week, Blackstone River flows increased as the week progressed while remaining elevated over historical median levels. In response to the heavy rainfall, surface salinity decreased this week, averaging 3.8 ppt with a maximum value of 12.8 ppt. Bottom salinity averaged 15.4 ppt, with a maximum value of 30.1 ppt. Water temperatures averaged 22.5°C on the surface and 22.3°C on the bottom. Temperatures ranged from 19.0°C to 25.7°C at the surface and from 19.0°C to 24.8°C at the bottom.
This week, surface dissolved oxygen (DO) averaged 7.5 mg/L, with a minimum of 3.8 mg/L. Bottom DO generally increased over the course of the week, averaging 4.1 mg/L and ranging from <1.0 mg/L to 10.1 mg/L. Bottom water hypoxia (DO ≤ 2.9 mg/L) was persistent throughout the first half of the week. Chlorophyll concentrations were slightly lower than the previous week, averaging 5.2 ug/L on the surface and 3.5 ug/L on the bottom, with a surface maximum of 16.2 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
Water quality at Bullock Reach was fair-to-poor this week. Overall, salinity remained similar over the course of the week, averaging 22.4 ppt at the surface, 28.7 ppt at mid-depth, and 31.0 ppt in bottom waters. Lowest salinity (15.5 ppt) occurred in surface waters, while greatest salinity (32.3 ppt) occurred in bottom waters. Temperatures averaged 23.2°C, 23.0°C, and 22.2°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 20.5°C to 25.7°C, mid temperatures ranged from 21.2°C to 24.7°C, and bottom temperatures ranged from 20.5°C to 23.5°C.
This week, DO averaged 7.2 mg/L at the surface, 4.0 mg/L at mid-depth, and 3.4 mg/L at the bottom. Hypoxic conditions (DO ≤ 2.9 mg/L) were observed at the mid and bottom depths. The minimum DO value, 1.7 mg/L, occurred in bottom waters during the morning of August 31, which was during a period of prolonged hypoxia that lasted approximately 13 hours. Chlorophyll concentrations averaged 15.2 ug/L at the surface and 10.8 ug/L at mid-depth. The maximum chlorophyll value in surface waters was 35.4 ug/L.
