Historical News
R/V Monitor's Blog
On Wednesday, August 4th, the crew of the R/V Monitor was out on the upper Bay collecting bacteria samples, taking Secchi Disk water clarity measurements, and conducting water column profiles using the Seabird instrument, all in an effort to document water quality improvements associated with NBC construction projects. The crew also serviced the Bullock's Reach buoy this day. Real-time surface mapping of water quality parameters as well as Par water clarity measurements were not conducted due to a faulty computer. Jeff captained the boat while monitoring professional Sara and summer intern Mackenzie collected the samples and data. It was a warm, humid and cloudy day with no wind and calm waters. The featured photo was taken of some shellfishers.
Phytoplankton Sampling
Phytoplankton samples were collected on July 28, 2021 at Bullock Reach and analyzed in the laboratory shortly after collection. It was a cloudy, misty day on Narragansett Bay with a cool breeze. Sondes data revealed the surface water temperature was 23.40°C, salinity was 20.74 psu, and chlorophyll a was 16.35 ug/L. The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light brown color and had a quick filter time. There were some noticeable comb jellyfish in the sample. 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 10,108,000 cells per Liter. The flagellates were found at 1,444,000 cells/L. The most predominant phytoplankton genus was Leptocylindrus spp. at 5,100,000 cells/L. Many were found in chains of 4 cells. Other representative genera include Skeletonema spp., Chaetoceros spp., and Thalassiosira spp.
200x phase contrast image of Akashiwo sanguinea.
Fixed Site Network
Water quality at Phillipsdale Landing was fair-to-poor this week. Sondes were changed out for routine maintenance on July 20. Rainfall this week was low, totaling 0.16 inches at TF Green. However, Blackstone River flows remained elevated over historical median levels, based on heavy rainfall through the first two weeks of July. Water column salinity this week was higher than last week. Surface salinity averaged 3.4 ppt, with a maximum value of 15.5 ppt. Bottom salinity averaged 13.4 ppt, with a maximum value of 28.5 ppt. Water temperatures have continued to warm, averaging 23.2°C on the surface and 21.8°C on the bottom. Temperatures ranged from 21.4°C to 27.1°C at the surface and from 20.0°C to 24.4°C at the bottom.
This week, surface dissolved oxygen (DO) averaged 7.1 mg/L, with a minimum of 3.4 mg/L, while bottom DO averaged 4.5 mg/L, with a minimum of 0.9 mg/L. Bottom DO fluctuated with the tides. Intermittent hypoxic conditions (DO ≤ 2.9 mg/L) were observed in bottom waters throughout the course of the week. A maximum duration of hypoxia of approximately 8 hours occurred in the afternoon and evening of July 23. Chlorophyll concentration averaged 3.4 ug/L on the surface and 1.5 ug/L on the bottom, with a surface maximum of 10.4 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. Salinity generally increased over the course of the week, averaging 18.3 ppt at the surface, 26.2 ppt at mid-depth, and 29.8 ppt in bottom waters. Lowest salinity (10.1 ppt) occurred in surface waters, while greatest salinity (30.7 ppt) occurred in bottom waters. Temperatures averaged 23.8°C, 22.1°C, and 20.1°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 21.9°C to 26.5°C, mid temperatures ranged from 20.3°C to 25.2°C, and bottom temperatures ranged from 19.2°C to 21.2°C.
This week, DO averaged 7.6 mg/L at the surface, 3.5 mg/L at mid-depth, and 2.1 mg/L at the bottom. Hypoxic conditions (DO ≤ 2.9 mg/L) were observed at the mid and bottom depths. The minimum DO value, 1.2 mg/L, occurred in bottom waters during the afternoon of July 18, during a mid-July period of prolonged hypoxia which lasted for over 5 days. Chlorophyll concentrations averaged 22.9 ug/L at the surface, 10.6 ug/L at mid-depth, and 3.6 ug/L at the bottom. Chlorophyll values > 50 ug/L occurred intermittently in surface waters starting mid-week.
Water Column Profiles
Water column profiles were conducted at eight locations in the Providence and Seekonk Rivers using a Seabird profiling instrument on June 9, 2021. Conditions leading up to sampling were relatively dry, with no recorded rainfall at T.F. Green. Evidence of density stratification was observed at five locations: Pomham Rocks, Point St. Bridge, Phillipsdale Landing, Conimicut Point, and Bullock Reach Buoy.
Surface salinities among all sites surveyed ranged from 6.7 psu at Phillipsdale Landing to 19.6 psu at Conimicut Point. Bottom salinities ranged from 21.3 psu at Pawtuxet Cove to 30.4 psu at Conimicut Point. Surface water temperatures ranged from 22.2°C at Point Street Bridge to 23.9°C at Pawtuxet Cove. Bottom water temperatures ranged from 14.1°C at Conimicut Point to 21.0°C at Pawtuxet Cove.
Dissolved oxygen (DO) ranged from a minimum of 3.3 mg/L near the bottom of Edgewood Yacht Club to 10.3 mg/L in the surface waters at Pawtuxet Cove. Hypoxic conditions (e.g., DO concentrations <2.9 mg/L) were not observed at any of the sites. Highest florescence occurred in the surface waters at Pawtuxet Cove. Please note that due a quality control issue, numerical fluorescence data are not posted at this time.
Water Column Profiles
Water column profiles were conducted at six locations in the Providence River using Seabird profiling instrument on June 3, 2021. In the five days prior to the survey, conditions were moderately wet with 0.79 inches of precipitation recorded at T.F. Green. Evidence of density stratification was observed across all sites.
Surface salinities among all the sites surveyed ranged from 7.5 psu at Pawtuxet Cove to 20.2 psu at Conimicut Point. Bottom salinities ranged from 21.4 psu at Pawtuxet Cove to 29.6 psu at both India Point Park and Conimicut Point. Surface water temperatures ranged from 16.7°C at India Point Park to 18.0°C at Edgewood Yacht Club. Bottom water temperatures ranged from 13.9°C at Conimicut Point to 16.6°C at Pawtuxet Cove.
Maximum and minimum dissolved oxygen (DO) concentrations were both observed at Edgewood Yacht Club. At this site, DO ranged from 4.2 mg/L in the bottom waters to 10.9 mg/L at the surface. Hypoxic conditions (e.g., DO concentrations <2.9 mg/L) were not observed at any of the sites. Highest florescence occurred in the surface waters at Edgewood Yacht Club. Please note that due a quality control issue, numerical fluorescence data are not posted at this time.
