Chaetoceros convolutus

General Close


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

Shape Bullet-shaped with large Close


In some diatoms, "closed or solid structures projecting from the cell wall;" in dinoflagellates, solid projections that usually taper to a point.

Size Large diameter 10 - 27 μm, length 25 - 60 μm
Colour Yellow-brown
Connection Direct contact between adjacent spines
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, present in cell and in spines
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.


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 Known to kill fish and crabs through mechanical irritation of the gills
Habitat Oceanic
Geographic Close


Widely distributed; occurring in many parts in the world.

, more common in temperate regions
Seasonal Abundant in spring and 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).

25 - 34
Temperature -2 - 25 °C


*Sometimes referred to as C. convolutum (Guiry 2012).


Empire Eukaryota
Kingdom Chromista
Subkingdom Harosa
Infrakingdom Heterokonta
Phylum Ochrophyta
Subphylum Khakista
Class Bacillariophyceae
Subclass Coscinodiscophycidae
Order Chaetocerotales
Family Chaetocerotaceae
Genus Chaetoceros
Species C. convolutus Castracane 1886

(Guiry and Guiry 2012)


Photosynthetic. Reproduces sexually and asexually (Guiry 2012).


Cells are bullet-shaped and usually in straight or slightly bent chains, connected by direct contact between adjacent spines. The two Close


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

have different shapes: The top valve is rounded and has spines arising from its centre, while the bottom valve is flat and has spines arising from just inside the Close


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

. The spines are long, thick, and hollow. They are a constant width throughout and are covered in numerous tiny "spinelets". The large spines initially curve strongly towards the bottom, and then curve slightly away. Close


"In some diatoms, the space between the valves of adjacent cells in chains" (Horner 2002).

between adjacent cells are partly or completely covered by the spines. The Close


In diatoms, the portion of the cell wall between the two valves of a cell; made up of intercalary bands (bands closest to the valves) and connecting bands (bands in the middle of the girdle). In dinoflagellates, the equivalent of a cingulum or transverse furrow (Horner 2002).

is roughly ⅓ of the cell length, and there is a distinct notch between each valve and the girdle (Cupp 1943). Chloroplasts are numerous, present inside the cell as well as inside the spines (Haigh 2010). Cells are yellow-brown in colour.


Large diameter Close


(axis, spine) The region of the apex or point. Refers to the most anterior point or region of the cell (HPP 2003).

axis): 10 - 27 μm
Length Close

Pervalvar axis

The axis through the centre point of the two valves of a frustule. This axis is perpendicular to the valve face.

(pervalvar axis
): 25 - 60 μm
Spine length: up to 200 μm or more
(Hasle and Syvertsen 1997, Haigh 2010)

Similar species


Harmful effects

Known to cause fish and crab mortalities through mechanical irritation of the gills (Horner 2002, Haigh 2010, Tester and Mahoney 1995).
Oceanic (Cupp 1943).


Cosmopolitan, but more common in temperate regions (Hasle and Syvertsen 1997).
Common from late winter to summer off southern California, sometimes in very large numbers (Cupp 1943).
Abundant in spring and fall (Albright et al. 1992, Haigh 2010).

Growth conditions

Growth rate found to increase with increasing temperature, up to 18 °C (Harrison et al. 1992). Has been found in large numbers in natural waters with salinities of 25 - 34, in low concentrations at salinities of 17 - 22, and absent below salinity 17 (Albright et al. 1992). Can tolerate low light conditions, possibly due to the extra chloroplasts in the spines (Harrison et al. 1992, Haigh 2010). Often most abundant at depths of 12 - 15 m (Haigh 2010).

Environmental Ranges

Depth range (m): 0 - 470
Temperature range (°C): -1.926 - 24.767
Nitrate (μmol L-1): 0.223 - 28.280
Salinity: up to 35.488
Oxygen (mL L-1): 4.806 - 9.192
Phosphate (μmol L-1): 0.074 - 2.337

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): 1.714 - 59.039
(OBIS 2012, cited in EOL 2012)

Bloom characteristics

Information not available.


Albright, L. J., Johnson, S. and Yousif, A. 1992. Temporal and spatial distribution of the harmful diatoms Chaetoceros concavicornis and Chaetoceros convolutus along the British Columbia coast. Canadian Journal of Fisheries and Aquatic Sciences. 49(9): 1924-1931.

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. Chaetoceros convolutus. Accessed 18 Mar 2012.

Guiry, M. D. 2012. Chaetoceros convolutus Castracane, 1886. Accessed 18 Mar 2012.

Guiry, M. D. and Guiry, G. M. 2012. Chaetoceros convolutum Castracane. Accessed 18 Mar 2012.

Haigh, N. 2010. Harmful Plankton Handbook. Nanaimo, BC, Canada. 52.

Harrison, P. J., Thompson, P. A., Guo, M. and Taylor, F. J. R. 1992. Effects of light, temperature and salinity on the growth rate of harmful marine diatoms, Chaetoceros convolutus and C. concavicornis that kill netpen salmon. Journal of Applied Phycology. 5: 259-265.

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.

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. Chaetoceros convolutum. Accessed 18 Mar 2012.

Tester, P. A. and Mahoney, B. 1995. Implication of the diatom, Chaetoceros convolutus, in the death of red king crab, Paralithodes camtschatica, Captains Bay, Unalaska Island, Alaska. In: Lassus, P., Arzul, G., Erard-Le Denn, E., Gentien, P. and Marcaillou-Le Baut, C. (eds.) Harmful Marine Algal Blooms. Lavoisier, Paris, France. 95-100.

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