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Phytoplankton of the Month

 
Photo of Thalassiosira
July 2012

Thalassiosira

Thalassiosira is a large, ca. 100 species, of centric, mostly marine diatoms. A few species occur in brackish to freshwater. The cells are discoid to cylindrical, solitary or joined in chains by threads composed of chitin. The valve face has areolae arranged in radial or tangential rows or arcs. Narrow tubes called strutted processes and composed of silica protrude through the silica cell wall. Their arrangement is used as a major taxonomic character. Organic threads may be extruded from the strutted processes, but their presence or absence is not a good taxonomic character. In the Pacific Northwest, Thalassiosira species are often abundant and occur early in spring as part of the spring bloom. Some Thalassiosira species are known to produce aldehydes that may be detrimental to the zooplankton, often copepods, who graze on them, although, ordinarily, Thalassiosira species are a harmless member of the phytoplankton community.

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Photo of Protoceratium reticulatum

Photo from: http://media.nordicmicroalgae.org/large/Protoceratium reticulatum_2.jpg
A. LM, two focal planes; B. LM, cyst; C. SEM, whole cell with ventral pore (arrow).

April 2013

Protoceratium reticulatum

Protoceratium reticulatum has polyhedral shaped cells with strong reticulations that often mask the plates; cells small to medium, 25-55 µm long, 25-35 µm wide. The epitheca a broad cone with ± straight sides, shorter than hypotheca; hypotheca with straight to convex sides, rounded to squarish antapex with no spines. Cingulum nearly medium, slightly descending. Chloroplasts present and give the cells a deep brown color.

Cells are easily confused with other smallish, round, brown cells including solitary Alexandrium cells and some Gonyaulax species. Populations from South Africa were described as Gonyaulax grindleyi Reinecke which remains a synonym. Cysts, described as Operculodinium centrocarpum (Deflandre & Cookson) Wall (also known as Hystrichosphaeridium centrocarpum Deflandre & Cookson) are spherical with dense ornamentation of tapering spines with hooked tips.

Their distribution is neritic, estuarine; cold temperate to subtropical waters; reported from all oceans. They produce yessotoxins which are toxic to mice when administered orally, but their threat to human health is currently unclear.

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Photo of Scrippsiella trochoidea

Figs from: http://nordicmicroalgae.org/taxon/Scrippsiella%20trochoidea
A. Scrippsiella cells B. Scrippsiella cysts
Photographer/artist Mats Kuylenstierna

July 2014

Scrippsiella trochoidea

Scrippsiella trochoidea are small to medium sized pear-shaped cells that are 16-36 µm long and are 20-23 µm wide. The epitheca, the top half of the cell, is conical with an apical horn (in contrast to Alexandrium and Heterocapsa) that is often clear while the hypotheca, the bottom half of the cell, is round with no projections or horns (in contrast to Gonyaulax). Their cingulum, or girdle band, is median, wide and strongly excavated. Scrippsiella has chloroplasts and does not grow in chains.

Their distribution is in estuarine, neritic, and cosmopolitan in temperate waters. Scrippsiella may form blooms in summer. They are not known to be toxic. Scrippsiella forms spherical to ovoid calcareous cysts.

Cells are often confused with other small, round, brown dinoflagellates including Gonyaulax spinifera, Alexandrium, and Heterocapsa.

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Photo of Noctiluca scintillans by Dr. Vera Trainer and Brian Bill, NOAA Photo of Noctiluca scintillans bloom

Photo of Noctiluca scintillans red bloom Photo of Noctiluca scintillans by Dr. Vera Trainer and Brian Bill, NOAA

Photo credit: top left and bottom right: Dr. Vera Trainer and Brian Bill, NOAA; top right: Teri King, Washington Sea Grant; bottom left: Dan Hanson, Hood Canal resident

August 2014

Noctiluca scintillans

Noctiluca scintillans is an unarmoured dinoflagellate with cells ranging in size from 200 to 2,000 µm in diameter. Their cytoplasm may contain photosynthetic symbionts. Since chloroplasts are absent in Noctiluca, they obtain their food by engulfing prey items (phagotrophy) that include diatoms, other dinoflagellates, ciliates, and fish eggs. A tentacle on the organism helps capture the prey.

Noctiluca's distribution is neritic and cosmopolitan in cold and temperate waters. They may form extensive tomato soup colored blooms during the warm calm summer months. Noctiluca, which means "night light," often produces a brilliant display of bioluminescence when the water is disturbed at night. Because it is very buoyant, it is frequently blown into windrows on the water or into bands of orange-red scum along the shore. It has been reported that large blooms may produce high levels of ammonium that could be toxic to fish.

For more information on Noctiluca see: http://wsg.washington.edu/mas/pdfs/SafeShellfishBooklet.pdf A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Photo of Akashiwo sanguinea by T. King, Washington Sea Grant

Photo credit: T. King, Washington Sea Grant

September 2014

Akashiwo sanguinea

Akashiwo sanguinea are medium sized (40-80 um long) unarmored dinoflagellates. The top half of the cell is broadly conical shaped while the bottom half of the cell is bilobed. They are dorso-ventrally flattened and have a deep longitudinal depression present in the middle of the cell. Their nucleus is large and frequently visible. Chloroplasts radiate out from the center of the cell.

A. sanguinea distribution is neritic and cosmopolitan in warm and temperate waters. Large blooms form in shallow estuaries in the late summer- early fall, often observed with Ceratium fusus. A. sanguinea has been reported to kill shellfish possibly due to the clogging of shellfish ctenidia (gills) or by oxygen depletion when the blooms decay and has also been implicated in shore bird deaths along the Washington and Oregon State coasts in 2009.

For more information see:
A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)
White, A.E., Watkins-Brandt, K.S., McKibben, S.M., Wood, A.M., Hunter, M., Forster, Z., Du, X., and W.T. Peterson. 2014. Large scale bloom of Akashiwo sanguinea in the Northern California current system in 2009. Harmful Algae 37:38-46.

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Photo of Dinophysis acuminata by Dr. Vera Trainer and Brian Bill, NOAAPhoto of Dinophysis acuminata by Dr. Vera Trainer and Brian Bill, NOAA
Photo of Dinophysis acuminata by Dr. Vera Trainer and Brian Bill, NOAA

Photo credit: Dr. Vera Trainer and Brian Bill, NOAA

October 2014

Dinophysis acuminata

Dinophysis acuminata are smaller sized (38-50µm long and 30-35 µm wide) armored dinoflagellates. The top of the cell (epitheca) is low and either flat or weakly convex while the bottom (hypotheca) is rounded and sometimes has small protuberances (bumbs) along the bottom edge. The side wing (left sulcal list) of the cell is supported by three ribs and extends down slightly over half of the cell length. Their chloroplasts are reddish-brown in color.

Their distribution is neritic in cold to warm temperate waters worldwide and are often present in late spring to summer. They produce dinophysis toxins and okadaic acid causing Diarrhetic Shellfish Poisoning in humans.

For more information see:
A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Photo of Asterionellopsis glacialis by Dr. Vera Trainer and Brian Bill, NOAAPhoto of Asterionellopsis glacialis by Dr. Vera Trainer and Brian Bill, NOAA

Photo credit: Dr. Vera Trainer and Brian Bill, NOAA

November 2014

Asterionellopsis glacialis

Asterionellopsis glacialis are pennate diatoms that are joined by the valve faces of elongated foot poles to create a spiraled, star-shaped chain (30-150um long). The foot pole narrows to form an elongated extension (neck). The foot pole is triangular in girdle view and rounded in valve view. One to two chloroplasts are present only in the foot pole.

Asterionellopsis glacialis's distribution is cosmopolitan, and is sometimes abundant in cold to temperate waters. They are frequently members of the surf zone diatom community.

For more information see:
A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Photo of Chaetoceros debilis by Dr. Vera Trainer and Brian Bill, NOAA

Photo credit: Dr. Vera Trainer and Brian Bill, NOAA

December 2014

Chaetoceros debilis

Chaetoceros debilis are centric diatoms that are 8-40 um wide, that connect into twisted chains. The ends of the cell walls are either flat or slightly concave with rounded corners. The spaces between the cells appear almost rectangular and slightly compressed. The spines start from inside the cell and extend outwards.

Chaetoceros debilis's distribution is cosmopolitan in cold waters.

For more information see:
A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Photo of Eucampia chain by Dr. Vera Trainer and Brian Bill, NOAA Photo of Eucampia chain segment by Dr. Vera Trainer and Brian Bill, NOAA

Left image: Eucampia chain; Right image: Eucampia chain segment
Photo credit: Dr. Vera Trainer and Brian Bill, NOAA

January 2015

Eucampia zodiacus Ehrenberg

Eucampia zodiacus are centric diatoms, 10-61µm long, with their cells joined together by flat projections forming beautiful helical chains. Eucampia has many girdle bands, but they are difficult to see. On the other hand, their disc shaped chloroplasts are quite visibly distributed throughout the cell.

Eucampia are found everywhere except in polar waters.

For more information see:
A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Photo of Protoperidinium oceanicum by Dr. Vera Trainer and Brian Bill, NOAA

Protoperidinium oceanicum
Photo credit: Dr. Vera Trainer and Brian Bill, NOAA

February 2015

Protoperidinium oceanicum

Protoperidinium oceanicum are large dinoflagellates, that are 200-300µm long and 150um wide. They have long horns extruding from the top and bottom of the cell. Red, heart-shaped cysts form within the organism, which makes it perfect as the February phytoplankton of the month!

P. oceanicum are found in oceanic, costal, temperate, and tropical waters.

For more information see:
A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Images of Azadinium by Urban Tillmann Images of Azadinium by Urban Tillmann
Image of Azadinium by B. Krock Image of Azadinium by B. Krock

March 2015

Azadinium spinosum

Azadinium spinosum are small dinoflagellates that are 12-16µm long and 7-11µm wide. They have a large posterior nucleus and a single chloroplast. These organisms can be mistaken for Heterocapsa and Scrippsiella. Azadinium produce Azaspiracid (AZA-1) and its derivatives (AZA2-30) causing Azaspiracid Poisoning (AZP) in humans. The first case occurred in the 1990s following an outbreak of human illness associated with ingestion of contaminated shellfish from Ireland. SoundToxins volunteers have been working for many years to find Azadinium in Puget Sound, however this cell can easily pass through a 20 µm-mesh phytoplankton net and must be identified in whole water samples.

Azadinium species, including A. spinosum, A. poporum and A. obesum, were identified at several sites throughout Puget Sound in the summer of 2014 using molecular probes. Low levels of AZA-2 were measured in plankton samples collected from Sequim Bay in the summer of 2012.

For more information see
NOAA’s Azadinium Fact Sheet (http://products.coastalscience.noaa.gov/pmn/_docs/Factsheets/Factsheet_Azadinium.pdf)

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Image of Stephanopyxis by Charles Krebs
Photo credit: Charles Krebs

April 2015

Stephanopyxis palmeriana

Stephanopyxis palmeriana are centric diatoms, approximately 27-71µm in diameter, and oblong in shape. These little rounded rectangles form chains that are connected by faint black external tubes protruding out of a slit within the diatom wall. Many chloroplasts are visible dotting the inside of their cells.

Stephanopyxis palmeriana are found in temperate to warm water.

For more information see
A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Image of Alexandrium by Brian Bill, NOAA Image of Alexandrium by Brian Bill, NOAA

Image of Alexandrium by Brian Bill, NOAA

Photo credit: Brian Bill, NOAA

May 2015

Alexandrium catenella

Alexandrium catenella is an armored dinoflagellate, approximately 24-24µm long and 22-44µm wide. Their round cells are identified by the shape and position of their pores and are often found in chains although solitary cells can also be observed.

This species is known to produce paralytic shellfish toxins (PSTs), which cause paralytic shellfish poisoning. Paralytic shellfish poisoning effects the neurological system and can result in tingling of the lips and tongue, loss of control of arms and legs, and respiratory arrest in humans if toxin levels are high. The accumulation of PSTs in shellfish is not a new phenomenon, nor is it one confined to Washington State. It has been occurring for hundreds of years in many parts of the world, primarily in temperate waters. Along the Pacific Coast, poisonous shellfish have been found all the way from Alaska to California. A member of Captain Vancouver's crew died in 1793 after eating toxic shellfish from an inlet in British Columbia, Canada, a place now known as Poison Cove. This was the first recorded PSP death in the Pacific Northwest. Native Americans were undoubtedly aware of the problem long before that, however. Washington State began intermittent testing for PSP in the 1930's with a more robust program beginning in 1957 after five Washington State residents suffered from PSP, three of whom died.

Alexandrium catenella can form resting cysts, when conditions are unfavorable, which allows for them to sit dormant for a period of time, re-emerging when environmental conditions are conducive to growth. The cysts are toxic and shellfish consuming these cysts can become toxic event when live cells of Alexandrium are not present in the water column. More information on Alexandrium cyst mapping in Puget Sound

The Washington Department of Health actively monitors and routinely closes shellfish harvesting areas when toxin levels are at or above 80 µg/100 g of shellfish tissue. SoundToxins volunteers identify and count Alexandrium catenella cells and provide an alert to the Department of Health when cells are observed.

The genus Alexandrium includes approximately 30 species, including A. catenella and A. tamarense. A. tamarense has been observed in northern Puget Sound.

For more information about PSP and to learn how to harvest shellfish safely, please refer to the Washington Sea Grant document Gathering Safe Shellfish.

For more information on Alexandrium see
Gathering Safe Shellfish
A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Image of Ditylum by Brian Bill, NOAA Image of Ditylum by Brian Bill, NOAA
Left image: Ditylum chain; Right image: Ditylum resting spore
Photo credit: Brian Bill, NOAA

June 2015

Ditylum brightwellii

Ditylum brightwellii are diatoms, 80-130µm long. These cells can be found individually or in chains. Depending on how you view them, they are rectangular in girdle view and triangular in valve view. In both views, you will be able to see the ridges on the outskirts of the cell. Ditylum has many small, evenly distributed, speckled chloroplasts. These organisms can create resting spores that are easy to spot. The cell is clear except for the spore found within each singular cell.

Ditylum are found everywhere except in polar waters.

For more information on Ditylum see
A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Image of large cell Pseudo-nitzschia by Brian Bill, NOAA Image of small cell Pseudo-nitzschia by Brian Bill, NOAA
Left image: Large size cells of Pseudo-nitzschia; Right image: Small size cells of Pseudo-nitzschia
Photo credit: Brian Bill, NOAA

July 2015

Pseudo-nitzschia spp.

Pseudo-nitzschia spp. are pennate diatoms. For the purposes of SoundToxins, we categorize them into two size classes: Large size cells (P. australis, P. heimii, P. fraudulenta, P. pungens, P. multiseries) which are generally 50-145 µm long and 2.5-10.0 µm wide and small size cells (P. pseudodelicatissima, P. delicatissima, P. cuspidata) which are generally 30 to 90 µm long and 1.0-2.0 µm wide.

The genus Pseudo-ntizschia includes approximately eight species that SoundToxins is looking for, including P. australis, P. multiseries, P. heimii, P. fraudulenta, P. pungens, P. pseudodelicatissima, P. delicatissima, and P. cuspidata.

This genus is known to produce domoic acid, a naturally occurring toxin. Domoic acid can be accumulated by both shellfish and finfish. Organisms can accumulate domoic acid without apparent ill effects; however, in humans the toxin interferes with nerve signal transmission. Also known as Amnesic Shellfish Poisoning (ASP), mild domoic acid poisoning symptoms can include nausea, vomiting, dizziness, and possibly short-term memory loss, while people poisoned with very high doses of the toxin can die.

Domoic acid poisoning via shellfish was first observed in Eastern Canada when three people died and 105 people became ill from eating contaminated blue mussels from Prince Edward Island in 1987. The toxin has since been identified along the West coast in fish and shellfish causing the closures of both recreational and commercial fisheries for extended periods of time. These closures have had serious economic impacts on the communities dependent on these fisheries.

The Washington Department of Health actively monitors and routinely closes shellfish harvesting areas when domoic acid levels are at or above 20 ppm, except in the viscera of Dungeness crab where the closure level is 30 ppm. SoundToxins volunteers identify and count Pseudo-ntizschia cells from whole water samples and provide an alert when the large size varieties are observed at cell counts over 50,000 cells/L and small size varieties are at cell counts over 1,000,000 cells/L.

For more information about Domoic Acid Poisoning, please refer to NOAA's Harmful Algal Blooms and Biotoxins page.

For more information on Pseudo-nitzschia see the following references:

A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

Fryxell, G.A., M.C. Villac, and L.P. Shapiro. 1997. The occurrence of the toxic diatom genus Pseudo-nitzschia (Bacillariophyceae) on the West Coast of the USA, 1920-1996: a review. Phycologia 36:419-437

Hasle, G.R. and E.E. Syvertsen. 1996. Marine Diatoms, pp.5-385. In: C.R. Tomas (ed.) Identifying Marine Diatoms and Dinoflagellates, Academic Press, San Diego.

Hasle, G.R., C.B. Lange, and E.E. Syvertsen. 1996. A review of Pseudo-nitzschia, with special reference to the Skagerrak, North Atlantic, and adjacent waters. Helgolander Meeresunters. 50:131-175

Skov, J., N. Lundholm, O. Moestrop, and J. Larsen. 1999. Potentially toxic phytoplankton 4. The diatom genus Pseudo-nitzschia (Diatomophyceae/Bacillariophyceae). ICES Identificatioin Leaflets for Plankton. Leaflet No. 185. ICES, Copenhagen. 23 pp.

Lundholm, N. et al. 2003. A study of the Pseudo-nitzschia pseudodelicatissima/cuspidata complex (Bacillariophyceae): What is P. pseudodelicatissima? J. Phycol. 39:797-813

Lundholm, N. et al. 2006. Inter- and intraspecific variation of the Pseudo-nitzschia delicatissima complex (Bacillariophyceae) illustrated by rRNA probes, morphological data and phylogenetic analyses. J. Phycol. 42:464-481

Lundholm, N. et al. 2010. Cryptic and pseudo-cryptic diveristy among species of the diatom genus Pseudo-nitzschia based on nuclear, plastid and mitochondrial sequence data; including descriptions of P. hasleana sp. nov. and P. fryxelliana sp. nov.

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Image of Ceratium fusus by Brian Bill, NOAA
Photo credit: Brian Bill, NOAA

August 2015

Ceratium fusus

Ceratium fusus are dinoflagellates, approximately 200-300µm long and 15-30µm wide. These singular cells are fusiform in shape with one end of the cell slightly tapering and curving towards the left, while the other end slightly tapering and curving towards the right. Linear markings are found towards the middle of the cell.

Ceratium fusus are found in temperate and tropical waters.

For more information on Ceratium fusus see:

A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Image of Polykrikos by J. Runyan, Washington Sea Grant
Photo credit: J. Runyan, Washington Sea Grant

September 2015

Polykrikos

Polykrikos are unarmored dinoflagellates, approximately 100-150µm long and composed of 2-8 zooids. Zooids are a single organism that makes up a colonial organism. Their barrel shape does not show the separation between the zooids. Stinging cells and food vacuoles are present. Chloroplasts are absent. Polykrikos hunt diatoms and dinoflagellates.

Polykrikos are found in temperate waters such as Puget Sound.

For more information on Polykrikos see:

A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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scanning electron microscopy image of Skeletonema by Brian Bill, NOAA Light microscopy image of Skeletonema by Brian Bill, NOAA Light microscopy image of Skeletonema by J. Runyan, Washington Sea Grant
Top: scanning electron microscopy image, Bottom: Light microscopy images

Photo credit: Top and left image: Brian Bill, NOAA; Right image: J. Runyan, Washington Sea Grant

October 2015

Skeletonema

Skeletonema are circular diatoms approximately 2-21µm in diameter. External tubes join the cells together to form long chains. The spaces between the cells may be short or long. Each cell has two chloroplasts.

Skeletonema are found off the coast all over the world, except in polar seas.

For more information on Skeletonema see:

A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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P. gracile by Brian Bill, NOAA P. micans by Brian Bill, NOAA
Left image: P. gracile; Right image: P. micans

Photo credits: Brian Bill, NOAA

November 2015

Prorocentrum spp.

Prorocentrum are small to medium sized dinoflagellates with a theca (shell) made up of two lateral plates. The two species of Prorocentrum vary in shape- teardrop shaped with a rounded end (P. gracile) or a broad leaf shaped with a pointed end (P. micans,). Both have a small spine present on the anterior. Chloroplasts are present.

Prorocentrum are found in temperate to tropical waters.

For more information on Prorocentrum see:

A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Dictyocha by Rita Horner
Photo credit: Rita Horner

December 2015

Dictyocha fibula

Dictyocha are small to medium, star shaped silicoflagellates. They are 10-45µm in size, not including their spine length. Their skeleton is composed of silica and their chloroplasts are golden brown in color. Taxonomy is based upon the structure of the skeletons, but they do vary in shape. They are solitary cells.

Dictyocha are found in warm and cold coastal and oceanic seas.

For more information on Dictyocha see:

A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Chaetoceros socialis by Gabriela Hannach, King County Environmental Lab Chaetoceros socialis by Gabriela Hannach, King County Environmental Lab
Chaetoceros socialis by Karlista Rickerson

Photo credit: top left and right, Gabriela Hannach, King County Environmental Lab; bottom, Karlista Rickerson (click images for larger view)

January 2016

Chaetoceros socialis

Chaetoceros socialis are small diatoms joined in petite, bendable chains. They are 4-15µm wide with their hair-like setae coming from the inside corners of the cell. C. socialis are generally found in a spherical shape.

Chaetoceros socialis are cosmopolitan.

For more information on Chaetoceros see:

A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Leptocylindrus danicus by Gabriela Hannach, King County Environmental Lab
Leptocylindrus danicus by Karlista Rickerson
Photo credit: top: Gabriela Hannach, King County Environmental Lab; bottom: Karlista Rickerson

February 2016

Leptocylindrus danicus

Leptocylindrus danicus are centric diatoms, approximately 5-16µm wide. These cylindrical cells form long chains connected by the entire valve surface. These valve surfaces are either convex or concave fitting into the other convex/concave cell wall. They have small oval shaped chloroplasts distributed throughout the cell.

Leptocylindrus danicus are cosmopolitan and are considered a common north temperate species.

For more information on Leptocylindrus danicus see:

A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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Ceratium furca by Brian Bill, NOAA
Photo credit: Brian Bill, NOAA

March 2016

Ceratium furca

Ceratium furca are large dinoflagellates, approximately 70-100µm long and 30-50µm wide. The cell is widest at the girdle. C. furca’s epitheca tapers to one point, while its hypotheca extends into two unequal points, where the right is shorter than the left. This organism sometimes blooms in the late summer to early fall. Ceratium lineatum looks similar to C. furca, but is much smaller in size (30-60µm long and 25-45µm wide).

Ceratium furca are found in temperate and tropical waters.

For more information on Ceratium furca see:

A Taxonomic Guide to Some Common Marine Phytoplankton, by Rita Horner (Biopress Ltd. 2002)

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