News – Page 31 – Narrabay

Week of December 10 – 16, 2023

Phytoplankton samples were collected on December 13, 2023 at Bullock’s Reach and analyzed in the laboratory shortly after collection. It was calm and brisk on Narragansett Bay with an outgoing tide. The qualitative tow net sample had a moderate filter time, and the filtrate was a light brown color with some particulate matter. The analysis of the quantitative whole water sample revealed a total of 81,000 cells per liter. The micro flagellates were found at 11,000 cells/L. The most predominant phytoplankton genus was Skeletonema spp. at 31,000 cells/L. Other representative genera include Leptocylindrus spp. and Guinardia spp. The photo featured this week is a 200x phase-contrast image of Staurastrum, a type of green algae in the desmid family. It gets its name from the Greek “stauron” which means cross and “astron” which means star. It is made of highly constricted unicells that are radially symmetrical and can be distinguished by cell wall patterns. Staurastrum is a food source for zooplankton in the aquatic food web.

Week of November 26 – December 2, 2023

Phytoplankton samples were collected on November 30, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. It was sunny and brisk on Narragansett Bay with calm conditions and a southwest wind at less than 10 kts. The qualitative tow net sample had a quick filter time, and the filtrate was a light tan color. The analysis of the quantitative whole water sample revealed a total of 153,000 cells per liter. The microflagellates were found at 52,000 cells/L. The most predominant phytoplankton genus was Skeletonema spp. at 65,000 cells/L. Other representative genera include Chaetoceros spp. and Eucampia spp. Chaetoceros socialis (see image, 200x phase contrast) is a diatomic phytoplankton found in marine and brackish waters. These phytoplankton have a characteristic linear colonial growth habit and their very long, overlapping, spines are thought to minimize sinking rates.

Week of November 13 – 19, 2023

Phytoplankton whole water sample was collected on November 15, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. No qualitative tow-net sample was collected this day. It was calm, clear, and very brisk on Narragansett Bay with clear water about 6.2 meters down. Sonde data revealed the surface water temperature was 10.4°C, salinity was 24.8 psu, and chlorophyll a was 0.8 ug/L. The analysis of the quantitative whole water sample revealed a total of 77,000 cells per Liter. The microflagellates were found at 39,000 cells/L. The most predominant phytoplankton genus was Skeletonema spp. at 13,000 cells/L. Other representative genera include Leptocylindrus spp., Chaetoceros spp. and Pseudo-nitzchia spp.

March 6, 2024

Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on March 6, 2024. Rainfall totaling 3.16 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 2.9 meters. The lowest clarity this week (2.3 meters) was measured at Phillipsdale Landing, while the greatest clarity (3.7 meters) was measured at Conimicut Point. There was no evidence of a north-to-south gradient of increasing water clarity among the sites this week.

May 14, 2024

Water clarity was measured at seven locations in the Providence River and Seekonk River estuary on May 14th, 2024. Rainfall totaling 0.1 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 2.4 meters, compared to 1.3 meters on the previous survey (December 13th). The lowest clarity this week (1.4 meters) was measured at Phillipsdale Landing, while the greatest clarity (3.4 meters) was measured at Bullock’s Reach. There was a general north-to-south gradient of increasing water clarity among the sites this week.

May 22, 2024

Water clarity was measured at seven locations in the Providence River and Seekonk River estuary on May 22nd, 2024. Rainfall totaling 0.27 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 2.1 meters, compared to 2.4 meters on the previous survey (May 14th). The lowest clarity this week (1.0 meters) was measured at Phillipsdale Landing, while the greatest clarity (3.2 meters) was measured at Conimicut Point. There was a general north-to-south gradient of increasing water clarity among the sites this week.

Week of October 29 – November 4, 2023

Phytoplankton samples were collected on November 1, 2023 at Bullock Reach and analyzed in the laboratory shortly after collection. It was cloudy and brisk on Narragansett Bay with a northwest wind at 10 kts. Sonde data revealed the surface water temperature was 13.08°C, salinity was 22.63 psu, and chlorophyll a was 1.06

ug/L. The qualitative tow net sample had a moderate filter time, and the filtrate was a light yellow-brown color. The analysis of the quantitative whole water sample revealed a total of 119,000 cells per liter. The micro flagellates were found at 62,000 cells/L. The most predominant phytoplankton genus was Skeletonema spp. at 46,000 cells/L. Other representative genera include Leptocylindrus spp., Eucampia spp., and Prorocentrum spp. Prorocentrum micans (see image, 200x phase contrast) is a tear-dropped shaped dinoflagellate that is often found in Narragansett Bay during the late summer-autumn time period. This species can form extensive blooms but is considered harmless.

Week of December 25 – 31, 2023

Nutrient samples were collected from 7 river stations on December 27th. In the five days prior to sampling, there were 0.04 inches of precipitation recorded at T.F. Green.

Among the stations sampled, the highest total nitrogen (TN) concentration was observed at Blackstone River @ Bikepath Bridge (835 ppb); the highest total dissolved nitrogen (TDN) and dissolved inorganic nitrogen (DIN) concentrations were at Pawtuxet River @ Broad St. (TDN = 962 ppb, DIN = 701 ppb). The lowest TN, TDN, and DIN were observed at Woonasquatucket River @ Valley St (TN = 650 ppb, TDN = 652 ppb, DIN = 504 ppb, average of duplicates).

The next scheduled sampling date is January 10, 2024.

December 10-16, 2023

Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on December 13th, 2023. Rainfall totaling 2.29 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 1.3 meters, compared to 4.5 meters on the previous survey (November 30th). The lowest clarity this week (0.7 meters) was measured at Phillipsdale Landing, while the greatest clarity (1.9 meters) was measured at Conimicut Point. There was a general north-to-south gradient of increasing water clarity among the sites this week.

Week of December 11 – 17, 2023

Nutrient samples were collected from 11 river stations and 8 bay stations on December 13th. Edgewood Shoal was sampled at the surface and bottom; all other bay stations were sampled at the surface only. In the five days prior to sampling, there were 0.64 inches of precipitation on December 10th and 1.65 inches on December 11th recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN) and total dissolved nitrogen (TDN) concentrations were observed at Warren Reservoir/Kickemuit River (TN = 849 ppb, TDN = 825 ppb); the highest dissolved inorganic nitrogen (DIN) was at Moshassuck River @ Footbridge at Mill St. (439 ppb). The lowest TN was at Pawtuxet River @ Broad St. (551 ppb), the lowest TDN was at Coles River @ Milford Rd (505 ppb), and the lowest DIN was at Palmer River @ Rt. 6 (115 ppb).

Among the bay stations sampled, the highest surface TN and TDN were observed at India Point Park (TN = 920 ppb, TDN = 742 ppb); the highest surface DIN was observed at Pomham Rocks (596 ppb). The lowest surface TN and DIN were observed at Pawtuxet Cove (TN = 614 ppb, DIN = 380 ppb), while the lowest surface TDN was at Conimicut Point (524 ppb). Chlorophyll a concentrations at the surface bay stations were low this week; concentrations averaged 0.311 μg/L overall with a maximum of 0.589 μg/L at Phillipsdale Landing.

The next scheduled sampling date is December 27, 2023.