Phytoplankton Sampling

Phytoplankton samples were collected on August 5, 2026 at Bullock Reach and analyzed in the laboratory shortly after collection.

The water temperature was 25.39 °C, the salinity was 21.83 psu, and the chlorophyll a was 18.18 ug/L.

It was clear, hot and sunny with murky water on this day. The qualitative tow net sample had a long filtration time. The filtrate was mostly clear with some suspended particulates and algae.

The analysis of the quantitative whole water sample revealed a total of 1,750,000 cells/L. The microflagellates were found at 146,000 cells/L. The most predominant phytoplankton genera were Skeletonema spp. at 980,000 cells/L, Eutreptiella spp. at 282,000 cells/L, and Chaetoceros spp. at 164,000 cells/L.

200x phase contrast image of Ebria spp.

Ebria spp. are phagotrophic flagellates which are present in marine coastal phytoplankton communities worldwide. The cells are solitary and hemispherical in shape. They have a distinctive internal silica skeleton with three main openings and two flagella..

Phytoplankton samples were collected on July 8, 2026 at Bullock Reach and analyzed in the laboratory shortly after collection.

The water temperature was 21.7 °C, the salinity was 27.4 PSU, and the chlorophyll a was 1.09 ug/L.

The qualitative tow net sample had a long filtration time. It had a dark brown coloration and contained jellyfish.

The analysis of the quantitative whole water sample revealed a total of 625,000 cells/L. The microflagellates were found at 367,000 cells/L. The most predominant phytoplankton genera were Thalassiosira spp. at 93,000 cells/L, Chaetoceros spp. at 60,000 cells/L, and Skeletonema spp. at 13,000 cells/L.

200x phase contrast image of Coscinodiscus spp.

Coscinodiscus is a widespread genus of solitary, disc-shaped diatoms. It is often regarded as one of the largest marine planktonic diatom genera with 400 – 500 described taxa. One singular freshwater species has also been identified.

Phytoplankton samples were collected on June 24, 2026 at Bullock Reach and analyzed in the laboratory shortly after collection.

It was sunny and clear on this day. The water temperature was 21.3 °C, the salinity was 27.2 PSU, and the chlorophyll a was 0.84 ug/L.

The qualitative tow net sample had a short filtration time and was cloudy and medium brown in coloration.

The analysis of the quantitative whole water sample revealed a total of 1,316,000 cells/L. The microflagellates were found at 1,106,000 cells/L. The most predominant phytoplankton genera were Cerataulina spp. at 110,000 cells/L, Skeletonema spp. at 27,000 cells/L, and Heterocapsa spp. at 23,000 cells/L.

200x phase contrast image of Chaetoceros lorenzianus

Chaetoceros lorenzianus is a species of centric diatom with a large diameter of 7 – 85 μm. Individual cells are usually joined in straight, stiff chains, connected by the touching of cell corners and fused adjacent spines. They have a wide distribution throughout the world and are commonly found throughout spring and summer in warm, shallow, marine waters.

Phytoplankton samples were collected on June 10, 2026 at Bullock’s Reach and analyzed in the laboratory shortly after collection.

On this day, the water temperature was 20.03 °C, the salinity was 27.2 PSU, and the chlorophyll a was 1.54 ug/L.

The qualitative tow net sample had a long filtration time and was cloudy and light golden brown in coloration.

The analysis of the quantitative whole water sample revealed a total of 5,570,000 cells/L. The microflagellates were found at 515,000 cells/L. The most predominant phytoplankton genera were Dactyliosolen spp. at 4,650,000 cells/L, Skeletonema spp. at 250,000 cells/L, and Chaetoceros spp. at 120,000 cells/L.

200x phase contrast image of Peridinium spp.

Peridinium spp. are cosmopolitan dinoflagellates mostly found in freshwater lakes, ponds and pools. Some inhabit brackish environments. This genus was originally described in the early 1830s, making it one of the first known groups of dinoflagellates. They are thought to be mixotrophic, which means they obtain energy through photosynthesis (autotrophy), and ingestion of small organisms (heterotrophy).

Phytoplankton samples were collected on May 26, 2026, at Bullock’s Reach and analyzed in the laboratory shortly after collection.

On this day, the water temperature was 18.12 °C, the salinity was 26.71 PSU, and the chlorophyll a was 1.68 µg/L.

The qualitative tow net sample had a short filtration time, and was cloudy and light brown in coloration.

The analysis of the quantitative whole water sample revealed a total of 2,932,000 cells/L. The microflagellates were found at 846,000 cells/L. The most predominant phytoplankton genera were Dactyliosolen spp. at 1,742,000 cells/L, Gonyaulax spp. at 246,000 cells/L, and Skeletonema spp. at 34,000 cells/L.

200x phase contrast image of Dactyliosolen spp.

Dactyliosolen is a type of cylindrical diatom which can be found sporadically in coastal waters throughout the year. They may be capable of storing nutrients, which would make them adaptable to living in environments where nutrient availability is variable. After sedimentation, blooms of this diatom can inhibit growth of benthic shellfish by clogging their gills.

Phytoplankton samples were collected on May 12, 2026 at Bullock’s Reach and analyzed in the laboratory shortly after collection.

On this day, the water temperature was 13.60 °C, the salinity was 22.93 PSU, and the chlorophyll a was 8.36 µg/L.

It was sunny and clear on this day. The qualitative tow net sample had a short filtration time and contained a large volume of copepods.

The analysis of the quantitative whole water sample revealed a total of 749,000 cells/L. The microflagellates were found at 673,000 cells/L. The most predominant phytoplankton genera were Silicoflagellate spp. at 40,000 cells/L, Skeletonema spp. at 13,000 cells/L, and Unknown Diatom spp. at 10,000 cells/L.

200x phase contrast image of Pediastrum spp.

Pediastrum is a genus of freshwater green algae found in lakes, ponds and along shores where water is rich in nutrients such as nitrogen. They are nonmotile and form flat colonies with concentric rings that resemble snowflakes. These groupings can both improve their buoyancy in the water column and help prevent predation.

Phytoplankton samples were collected on April 29, 2026 at Bullock Reach and analyzed in the laboratory shortly after collection.

On this day, the water temperature was 10.70 °C, the salinity was 24.63 PSU.

The qualitative tow net sample had a moderate filtration time. The filtrate was cloudy and reddish brown with some darker particulates.

The analysis of the quantitative whole water sample revealed a total of 2,224,000 cells/L. The microflagellates were found at 194,000 cells/L. The most predominant phytoplankton genera were Skeletonema spp. at 1,694,000 cells/L, Thalassiosira spp. at 128,000 cells/L, and Chaetoceros spp.at 92,000 cells/L.

200x phase contrast image of Asterionellopsis spp.

Asterionellopsis is a genus of neritic pennate diatom found in cold to temperate coastal waters. Their cells have two chloroplasts each and are joined by valve faces into star-shaped or spiraling chains.

Phytoplankton samples were collected on April 15, 2026 at Bullock Reach and analyzed in the laboratory shortly after collection.

It was sunny with light wind on this day. The water temperature was 12.66 °C, the salinity was 19.05 PSU, and the chlorophyll a was 15.54 ug/L.

The qualitative tow net sample had a moderate filtration time. The filtrate was cloudy and reddish brown.

The analysis of the quantitative whole water sample revealed a total of 37,240,000 cells/L. The microflagellates were found at 320,000 cells/L. The most predominant phytoplankton genera were Skeletonema spp. at 33,763,000 cells/L, Chaetoceros spp. at 1,653,000 cells/L, and Leptocylindrus spp. at 765,000 cells/L.

200x phase contrast image of Thalassiosira spp.

Thalassiosira is a large genus of mostly marine diatoms which are known for their bloom formations. They are responsible for significant algal blooms worldwide in temperate, boreal, and polar regions, particularly in layers underlying sea ice and in upwelling areas.

Phytoplankton samples were collected on October 15, 2025 at Bullock’s Reach and analyzed in the laboratory shortly after collection.

It was sunny and windy on this day. The water temperature was 16.13 °C and the salinity was 26.53 psu.

The qualitative tow net sample had a short to moderate filtration time. The filtrate was light tan and contained some dark precipitates.

The analysis of the quantitative whole water sample revealed a total of 69,000 cells/L. The microflagellates were found at 30,000 cells/L. The most predominant phytoplankton genera were Chaetoceros spp. at 31,000 cells/L, Prorocentrum spp. at 3,000 cells/L, and pennate diatoms at 3,000 cells/L.

Dinophysis acuminata is a marine phytoplankton species of dinoflagellates that is found in the coastal waters of Rhode Island and north Atlantic waters. This is one of several phototrophic species that are classed as toxic, as they produce okadaic acid which can cause diarrhetic shellfish poisoning (DSP).

Phytoplankton samples were collected on October 1, 2025 at Bullock’s Reach and analyzed in the laboratory shortly after collection.

It was sunny and breezy on this day. The water temperature was 20.14 °C, the salinity was 30.14 psu, and the chlorophyll a was 4.28 ug/L.

The qualitative tow net sample had a short to moderate filtration time. The filtrate was dark brown and contained some jellyfish.

The analysis of the quantitative whole water sample revealed a total of 509,000 cells/L. The microflagellates were found at 197,000 cells/L. The most predominant phytoplankton genera were Cerataulina spp. at 85,000 cells/L, Chaetoceros spp. at 65,000 cells/L, and Ditylum spp. at 32,000 cells/L.

Thalassiosira is a genus of centric diatoms that are vital primary producers in temperate and polar seas. They can thrive in low temperature and light, as well as mixed waters, which allows them to play a large part in spring diatom blooms. They are also able to defend themselves against zooplankton, allowing them to survive the predation that normally keeps phytoplankton blooms in check.