Thalassiosira rotula

General Close


(diatoms) Having radial symmetry, i.e., cell is shaped like a coin or a tuna can or a soup can.

Shape Coin-shaped
Size Diameter 8 - 60 μm, height 5 - 20 μm
Colour Yellow-brown
Connection Thick bundle of organic threads
Covering Silica Close


In diatoms, the hard and porous silica cell wall (Horner 2002).



(plural: flagella) A tail-like projection that sticks out from the cell body and enables movement.



An organelle in the cell that contains the cell pigments (Horner 2002). This is where photosynthesis occurs. A chloroplast is a specialized chromatophore.

Numerous, small, near cell wall
Lifestyle Close


The chemical process by which light energy, water and carbon dioxide are combined to produce oxygen and organic compounds. Photoautotrophic organisms (plants and algae) use this reaction to produce their own food.

. Sexual/asexual. Close


In diatoms, the special cells that restore normal size following cell division. Auxospores are associated with sexual reproduction (Horner 2002).



A rapid increase or accumulation of algal populations in an aquatic system. This will likely involve one or a few dominant phytoplankton species. This follows seasonal patterns (i.e., spring, summer or fall bloom) with dominant species being those that are best adapted to the environmental conditions of that time period. Discolouration of the water may be observed because of the algae's pigmentation. Blooms are often green but may be yellow-brown or red depending on the species present.

Information not available
Harmful effects Produces chemicals that can inhibit copepod reproduction
Habitat Close


Describing shallow, near-shore areas and the organisms that live there. Refers to shallow marine waters ranging from the low tide mark to the continental shelf. Varying amounts of sunlight penetrate the water, allowing photosynthesis by both phytoplankton and bottom-dwelling organisms. Close proximity to land favours high nutrient content and biological activity (Encyclopedia Britannica 2011).

Geographic Close


Widely distributed; occurring in many parts in the world.

Seasonal Abundant during late spring and early fall
Growth Conditions


The dissolved ion content of a body of water. Can be measured in the following units: parts per thousand (PPT or ‰), practical salinity units (PSU), and absolute salinity (g/kg). PPT is measured by weight, denoting the number of parts salt per thousand total parts or a value of 10-3. PSU measures the conductivity of saltwater and compares it in a ratio to a standard KCl solution (because this is a ratio, salinity measured in this way can also be written without units). The newest unit of salinity is absolute salinity, which uses the mass fraction of salt in seawater (g salt per kg seawater) rather than its conductivity (TEOS-20 2010).

29 - 36
Temperature -1 - 26 °C




Empire Eukaryota
Kingdom Chromista
Subkingdom Harosa
Infrakingdom Heterokonta
Phylum Ochrophyta
Subphylum Khakista
Class Coscinodiscophyceae
Subclass Coscinodiscophycidae
Order Thalassiosiranae
Family Thalassiosirales
Genus Thalassiosira
Species T. rotula Meunier 1910

(Guiry and Guiry 2012)


Photosynthetic. Reproduces sexually and asexually (Guiry 2012). Auxospores present (Cupp 1943).


Cells are widely Close



and connected in a chain by a thick bundle of threads. Threads extend from a cluster of central Close

Strutted process

(how is this different than marginal process?) In some diatoms, a narrow tube through the frustule that is usually associated with the secretion of chitin. It may appear as a marginal process or as a simple pore in the valve wall (Spaulding et al. 2010).

strutted processes
(Hasle and Syvertsen 1997). The Close


In diatoms, the structurally distinct halves of the cell wall (Becker 1996).



The outline or border that defines the shape of an organism or cell.

are slightly rounded, and each valve has one Close

Intercalary bands

Girdle bands that are furthest away from the valve (Smithsonian 2011).

intercalary band
which is unevenly thickened. Chloroplasts are numerous, small, and distributed near the cell wall (Cupp 1943).
The valve face is covered with Close


(symmetry) Describing a shape that many axes of symmetry. That is, it does not have a left and right like humans do (bilateral symmetry), but can be divided into equal halves no matter where you place the axis. Some examples of radially symmetrical organisms include sea stars and centric diatoms like Thalassiosira.



Features that provide support to other structures in the cell.

and the Close


In diatoms, "the part of a valve that extends from the valve face, forming the valve edge." It is visible when the frustule is viewed in girdle view (Spaulding 2010).

is covered with Close


In diatoms, the regularly repeated hexagonal holes on the valve walls (HPP 2003).

(Kraberg et al. 2010). One Close

Labiate process

In diatoms, a simple slit in the valve wall with two internal lips, one on each side of the slit. They can be useful in identification because they are positioned differently in different species (Horner 2002).

labiate process
with external tubes is present near the valve mantle. Additional strutted processes are also distributed throughout the valve surface (Horner 2002) and near the margins (Kraberg et al. 2010).


Diameter: 8 - 60 μm
Height: 5 - 20 μm
Valve areolae: 18 - 24 in 10 μm

Marginal process

In some diatoms, a long, coarse external tube through the frustule (Tomas 1997).

Marginal processes
: 12 - 15 in 10 μm
(Hasle and Syvertsen 1997, Kraberg et al. 2010)

Similar species

Other Thalassiosira species. T. rotula is easily distinguished by the thick bundle of central threads that connect adjacent cells.

Harmful effects

Produces high concentrations of polyunsaturated aldehydes (PUAs) that can inhibit copepod reproduction (Barreiro et al. 2011).


Neritic (Cupp 1943).


Cosmopolitan (Hasle and Syvertsen 1997).
Can be very abundant during spring and summer in Northern European seas (Kraberg et al. 2010).
Abundant during late spring and early fall, and present in low numbers throughout the summer.

Growth conditions

Optimal growth conditions in nature are estimated to be around 14 °C with light intensity of 2000 - 3000 Close


(abbreviated 'lx') Units for measuring light intensity in a given surface area.

(Schone 1972) and salinity of 20 - 33. Salinity below 20 or above 38 would likely damage or kill the cells (Schone 1974). May be favoured by high N levels (Hobson and McQuoid 2001). Often forms blooms during summer Close


A wind-driven mechanism of mixing the water column. Cold, dense, nutrient-rich, and often oxygen-poor water from depths rises to replace the warmer nutrient-poor surface water. This input of nutrients can have a significantly increase primary productivity in a region (Dugdale 1985).

(Raine et al. 1993).

Environmental Ranges

Depth range (m): 0 - 100
Temperature range (°C): -1.421 - 26.001
Nitrate (μmol L-1): 0.135 - 16.590
Salinity: 29.305 - 36.252
Oxygen (mL L-1): 4.705 - 8.401
Phosphate (μmol L-1): 0.048 - 1.441

Silicic acid

A general term to describe chemical compounds containing silicon, oxygen and hydrogen with a general formula of [SiOx(OH)4-2x]n. Diatoms polymerize silicic acid into biogenic silica to form their frustules (Azam and Chisholm 1976).

(μmol L-1): 0.754 - 31.065
(OBIS 2012, cited in EOL 2012)

Bloom characteristics

Information not available.


Barreiro, A. Carotenuto, Y., Lamari, N., Esposito, F., D'Ippolito, G., Fontana, A., Romano, G., Ianora, A., Miralto, A. and Guisande, C. 2011. Diatom induction of reproductive failure in copepods: The effect of PUAs versus non-volatile oxylipins. Journal of Experimental Marine Biology and Ecology. 401(1-2): 13-19.

Cupp, E. E. 1943. Marine Plankton Diatoms of the West Coast of North America. University of California Press. Berkeley, California. 238.

Encyclopedia of Life (EOL). 2012. Thalassiosira rotula. Accessed 19 Feb 2012.

Guiry, M. D. 2011. Thalassiosira rotula Meunier, 1910. Accessed 19 Feb 2011.

Guiry, M. D. and Guiry, G. M. 2012. Thalassiosira rotula Meunier. Accessed 19 Feb 2012.

Hasle, G. R. and Syvertsen, E. E. 1997. Marine diatoms. In: Tomas, C. R. (ed.) Identifying Marine Phytoplankton. Academic Press, Inc., San Diego. 5-385.

Hobson, L. A. and McQuoid, M. R. 2001. Pelagic diatom assemblages are good indicators of mixed water intrusions into Saanich Inlet, a stratified fjord in Vancouver Island. Marine Geology. 174(1-4): 125-138.

Horner, R. A. 2002. A Taxonomic Guide To Some Common Phytoplankton. Biopress Limited, Dorset Press, Dorchester, UK. 200.

Kraberg, A., Baumann, M. and Durselen, C. D. 2010. Coastal Phytoplankton: Photo Guide for Northern European Seas. Verlag Dr. Friedrich Pfeil, Munchen, Germany. 204.

Ocean Biogeographic Information System (OBIS). 2012. Thalassiosira rotula. Accessed 19 Feb 2012.

Raine, R., Joyce, B., Patching, J. W., McMahon, T. and Roden, C. 1993. Upwelling and the phytoplankton ecology of southwest Irish coastal waters. ICES, Copenhagen, Denmark. 18.

Schone, H. 1972. Experimental investigations on the ecology of the marine diatom Thalassiosira rotula. I. Temperature and light. Marine Biology. 13(4): 284-291.

Schone, H. 1974. Experimental investigations on the ecology of the marine diatom Thalassiosira rotula. II. Influence of salinity. Marine Biology. 27(4): 287-298.

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