Historical News
Phytoplankton Sampling
Phytoplankton samples were collected at Bullock's Reach on October 11, 2017 and analyzed in the laboratory shortly after collection. It was a cloudy day with a slight drizzle on Narragansett Bay. Water temperatures are beginning to decrease, and the temperature was 2°C cooler than the previous sampling date at 19.70°C. Salinity was 27.38 psu and chlorophyll a concentration was 2.7 µg/L, a decrease of over 3 µg/L compared to the previous sample.
The plankton tow net sample was filterable with a 20 micron mesh. The filtrate was a light tan color with a quick filter-ability 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.
Phytoplankton concentration was 670,000 cells/L, an increase by two times compared to the previous sampling. Interestingly, chlorophyll a concentration was much lower this week despite the higher abundance of cells. The most predominant phytoplankton genus was Leptocylindrus at 354,000 cells/L. The flagellates were found at 310,000 cells/L and other representative genera included Skeletonema and Chaetoceros.
200x phase contrast micrograph of Odontella spp. This diatom is in the middle of cell division. Can you see the newly forming frustule, or silica cell wall, inside the original parent cell?
R/V Monitor's Blog
The R/V Monitor was out on the upper Bay twice this week. First, on Tuesday, November 14th, the crew was out at the Bullock Reach buoy, servicing the sondes. Jeff captained the boat while monitoring professional Bekki and data analyst Karen serviced the sondes. It was a sunny but cool and breezy day, with choppy waters. Again, on Wednesday, November 15th, the crew was out collecting bacteria samples, taking Secchi Disk water clarity measurements, conducting water column profiles using the Seabird instrument, and conducting real-time surface mapping of water quality parameters, including dissolved oxygen, chlorophyll, water temperature, salinity and pH, all in an effort to document water quality improvements associated with NBC construction projects. Jeff captained the boat while monitoring professionals Steve and Sara collected the samples and data. It was a sunny but cool day with a breeze in the morning, which subsided a bit in the afternoon. The water was slightly choppy. The photo below shows a passing vessel this day.
Surface Mapping
Data was collected on November 15, 2017 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 low in areas surveyed. From north to south, average chlorophyll concentrations were as follows: Seekonk River (1.96 µg/l), Upper Providence River (1.40 µg/l), Edgewood Shoals area (1.29 µg/l), Pawtuxet River area (1.31 µg/l), and the Lower Providence River (1.38 µg/l). Overall, chlorophyll ranged between non-detectable and 7.8 µg/l with an overall average of 1.59 µg/l. The chlorophyll data from this date is presented in the map below:
Surface Mapping
Data was collected on November 8, 2017 while the R/V Monitor was underway collecting nutrient samples and performing vertical profiles in the Providence River estuary. The chlorophyll concentrations were low in areas surveyed. From north to south, average chlorophyll concentrations were as follows: Upper Providence River (2.15 µg/l), Edgewood Shoals area (2.38 µg/l), Pawtuxet River area (2.27 µg/l), and the Lower Providence River (2.57 µg/l). Overall, chlorophyll ranged between non-detectable and 5.9 µg/l with an overall average of 2.36 µg/l. The chlorophyll data from this date is presented in the map below:
Water Column Clarity
Water clarity was measured at only two locations in the Providence River on October 25, 2017; the survey was limited this week by rough weather and unsafe conditions for boat work. The survey was conducted during rainy conditions, with 0.38 inches of rainfall the day prior, and 1.4 inches of rainfall by the end of the sample day itself. Secchi depth was reduced at both sites surveyed compared to the previous week: Conimicut Point Secchi depth measured 1.7 m, compared to 4.2 m on 10/18 and Bullock Reach Secchi depth measured 1.9 m, compared to 3.1 m on 10/18.
