Phytoplankton Sampling

Phytoplankton samples were collected on March 19, 2025 at Bullock Reach and analyzed in the laboratory shortly after collection.

It was sunny and cold on this day. The water temperature was 6.6 degrees Celsius, and jellyfish were observed. Sonde data was not recorded.

The qualitative tow net sample had a moderate to long filtration time and the filtrate was cloudy and dark brown with a large amount of sediment.

The analysis of the quantitative whole water sample revealed a total of 4,744,000 cells/L. The microflagellates were found at 86,000 cells/L. The most predominant phytoplankton genera were Leptocylindrus spp. at 2,918,000 cells/L, Chaetoceros spp. at 1,474,000 cells/L, and Skeletonema spp. at 144,000 cells/L.

Pyrocystis spp., shown here in a 200x phase contrast micrograph, are non-motile, tropical, epipelagic marine dinoflagellates. They exhibit bioluminescence, which means emitting light through a chemical reaction, when they are disturbed or agitated. This is an unusual defense mechanism against predation which aims to startle grazers who would otherwise eat them.

Phytoplankton samples were collected on November 14, 2024 at Bullock Reach and analyzed in the laboratory shortly after collection.

It was partly sunny, windy and cold on this day. Sonde data was not recorded.

The qualitative tow net sample had a quick filtration time and the filtrate contained some light brown particulates and plant matter.

The analysis of the quantitative whole water sample revealed a total of 288,000 cells/L. The microflagellates were found at 30,000 cells/L. The most predominant phytoplankton genera were Chaetoceros spp. at 34,000 cells/L, Leptocylindrus spp. at 76,000 cells/L, and Heterocapsa spp. at 26,000 cells/L.

Staurastrum, shown here in a 200x phase contrast micrograph, is a large genus of microscopic green algae which are closely related to land plants. They are found in freshwater habitats around the world and live primarily in acidic lakes, ponds and swamps with low nutrient levels. Many Staurastrum species serve as indicators of eutrophic conditions.

Phytoplankton samples were collected on October 30, 2024 at Bullock’s Reach and analyzed in the laboratory shortly after collection. Weather conditions and Sonde data were not recorded on this day. The qualitative tow net sample had a moderate filtration time. The filtrate was slightly cloudy with some golden brown particulates. The analysis of the quantitative whole water sample revealed a total of 260,000 cells/L. The microflagellates were found at 100,000 cells/L. The most predominant phytoplankton genera were Chaetoceros spp. at 104,000 cells/L, Leptocylindrus spp. at 26,000 cells/L, and Skeletonema spp. at 18,000 cells/L. Proboscia alata, shown here in a 100x phase contrast micrograph, is a solitary or chain-forming diatom that can measure up to 1mm in length. They are identified by the presence of a proboscis with a truncated tip and offset claspers. These diatoms are an oceanic, temperate water species and are sometimes found near the coast.

Phytoplankton samples were collected on October 17, 2024 at Bullock’s Reach and analyzed in the laboratory shortly after collection. It was windy and brisk on Narragansett Bay. Sonde data revealed the surface water temperature was 14.63°C, salinity was 30.01 psu, and chlorophyll a was 2.58 ug/L. The qualitative tow net sample had a quick filtration time and the filtrate was clear. The analysis of the quantitative whole water sample revealed a total of 156,000 cells/L. The microflagellates were found at 48,000 cells/L. The most predominant phytoplankton genera were Prorocentrum spp. at 38,000 cells/L, Leptocylindrus spp. at 16,000 cells/L, and Cylindrotheca spp. at 12,000 cells/L. Corethron hystrix, shown here in a 200x phase contrast micrograph, is a solitary species of centric diatom found in the North Atlantic and North Pacific, typically in the spring and fall. They have a unique pill shape and two rings of long spines directed towards one end, and a crown of shorter, hooked spines pointed in the opposite direction. Although they do not bloom in large numbers, it has been observed that they may cause physical obstructions in the gills of farmed salmon.

​Phytoplankton samples were collected on October 3, 2024 at Bullock’s Reach and analyzed in the laboratory shortly after collection. Weather conditions and Sonde data were not recorded on this day. The qualitative tow net sample had a quick filtration time. The filtrate was slightly cloudy and reddish brown with some particulates. The analysis of the quantitative whole water sample revealed a total of 1,712,000 cells/L. The microflagellates were found at 112,000 cells/L. The most predominant phytoplankton genera were Heterocapsa spp. at 1,232,000 cells/L, Prorocentrum spp. at 108,000 cells/L, and Leptocylindrus spp. at 100,000 cells/L. Chaetoceros socialis, shown here in a 100x phase contrast micrograph, is a species of diatom belonging to one of the most diverse genera of marine planktonic organisms. Due to their high growth rates, research on the use of Chaetoceros species in biotechnology is ongoing. They are currently used in commercial aquacultures and studies suggest that they have enormous potential for producing biofuel.

Phytoplankton samples were collected on September 4, 2024 at Bullock Reach and analyzed in the laboratory shortly after collection. ​It was a sunny, calm and cloudless day on Narragansett Bay. Sonde data was not analyzed on this day. The qualitative tow net sample had a quick filtration time, the filtrate was slightly cloudy and golden brown with some black particulates. The analysis of the quantitative whole water sample revealed a total of 874,000 cells/L. The microflagellates were found at 94,000 cells/L. The most predominant phytoplankton genera were Skeletonema spp. at 240,000 cells/L, Leptocylindrus spp. at 224,000 cells/L, and Cylindrotheca spp. at 188,000 cells/L. Pleurosigma, shown here in a 200x phase contrast micrograph, is a widely distributed genus of elongate, biraphid diatoms which glide and rotate in brackish to marine waters. They are pelagic and either float on the tides, sink to lower levels on top of the salt layer or attach to marine organisms. These diatoms contribute to essential oxygen levels in the ocean and also serve as a food source for animal larvae and dinoflagellates.​​

​Phytoplankton samples were collected on August 21, 2024 at Bullock Reach and analyzed in the laboratory shortly after collection. It was sunny and breezy on Narragansett Bay. Sonde data revealed the surface water temperature was 22.0°C, salinity was 27.1 psu, and chlorophyll a was 7.0 ug/L. The qualitative tow net sample had a quick filtration time, the filtrate was a light tan color. The analysis of the quantitative whole water sample revealed a total of 433,000 cells/L. The microflagellates were found at 35,000 cells/L. The two most predominant phytoplankton genera were Skeletonema spp. at 84,000 cells/L and Leptocylindrus spp. at 79,000 cells/L. Other representative genera include Ceratulina spp., and Cylindrotheca spp. Today’s featured 200x phase-contrast micrograph shows Chaetoceros curvisetus, a species of marine phytoplankton that is widely distributed and common to North Atlantic waters. Chaetoceros serves as an important food source within the water column and major carbon contributor to the benthic environment. Chaetoceros has been reported to contribute about 91% of total phytoplankton cells serving as an important primary producer within this area.

Phytoplankton samples were collected on July 24, 2024 at Bullock Reach and analyzed in the laboratory shortly after collection. It was a cloudy and humid day on Narragansett Bay. Sonde data revealed the surface water temperature was 24.4°C, salinity was 26.8 psu, and chlorophyll a was 12.8 ug/L. The qualitative tow net sample had a medium filtration time and the filtrate was clear with a light brown color. Some particulates were noted in the filtrate. The analysis of the quantitative whole water sample revealed a total of 1,154,000 cells/L. The microflagellates were found at 672,000 cells/L. The most predominant phytoplankton genus was Eutreptiella spp. at 154,000 cells/L. Other representative genera include Prorocentrum spp. and Heterocapsa spp. Polykrikos spp. is a genus of marine dinoflagellates featured in today’s 200x phase contrast micrograph image. It gets its name from the Greek “poly” – many, and “krikos” – ring or circle. Polykrikos have been found to regulate algal blooms as they feed on toxic dinoflagellates. However, there is also some data available on Polykrikos being toxic to fish.​

​Phytoplankton samples were collected on July 10, 2024 at Bullock Reach and analyzed in the laboratory shortly after collection. Sonde data revealed the surface water temperature was 25.9°C, salinity was 23.6 psu, and chlorophyll a was 5.0 ug/L.  The qualitative tow net sample had a short filtration time, the filtrate was slightly cloudy, and the analyzed sample volume was 500 mL. The analysis of the quantitative whole water sample revealed a total of 999,000 cells/500 mL. The most predominant phytoplankton genus was Skeletonema spp. at 572,000 cells/500mL. Other representative genera include Chaetoceros spp. and Leptocylindrus spp. Ditylum is a genus of marine centric diatoms with a worldwide distribution in boreal, tropical, coastal and estuarine environments and is the feature 200x phase contrast micrograph image for the day. Ditylum spp. have been used as a model organism for genetic studies concerning metapopulation structures and environmental influence on population genetic variability.

​Phytoplankton samples were collected on June 12, 2024 at Bullock Reach and analyzed in the laboratory shortly after collection. Sonde data revealed the surface water temperature was 19.68°C, salinity was 24.22 psu, and chlorophyll a was 9.89 ug/L. The qualitative tow net sample had a short filtration time, and the filtrate was mostly clear. The analysis of the quantitative whole water sample revealed a total of 12,732,000 cells per Liter. The most predominant phytoplankton genus was Skeletonema spp. at 12,408,000 cells/L. Other representative genera include Chaetoceros spp. and Leptocylindrus spp. Prorocentrum spp. (see 200x phase contrast image below) is a dinoflagellate genus containing several toxic and harmful species. P. micans is one of the most common species in the genus. Prorocentrum is found in cold, temperate to tropical waters. This genus forms extensive red tides in many parts of the world, though blooms are usually harmless. It may excrete substances that inhibit diatom growth, but these substances do not enter the food chain or affect organisms at higher trophic levels.