Chaetoceros socialis

General Close


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

Shape Elliptic cylinder
Size Large diameter 2 - 15 μm, length 2 - 12 μm
Colour Yellow-brown
Connection Crossing of adjacent Close


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

and bundling of long 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.

One, plate-like, located in 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).

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

Resting spore

In diatoms, a cell that requires a dormancy period prior to germination and can survive for several years; usually developed to survive adverse conditions. They are commonly observed in centric but not pennate diatoms. The morphology of the spore may be similar or different from a vegetative cell; they usually have heavily silicified walls and are rich in storage products (Horner 2002).

Resting spores


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 May cause physical damage to fish gills
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).

and Close


The ecological zone at the bottom of a body of water.

Geographic Close


Widely distributed; occurring in many parts in the world.

with higher densities in colder waters
Seasonal Early spring to summer
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).

24 - 34 (optimal)
Temperature -2 - 29 °C


*Sometimes referred to as C. sociale (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. socialis Lauder 1864

(Guiry and Guiry 2012)


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


Cells occur in large, circular, mucous-covered colonies composed of many short chains. Cells are small and rectangular in girdle view. Adjacent cells are connected by crossing of the spines, without direct contact of the cell body. Close


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

between cells are long with a slight narrowing in the middle. Spines are thin and arise from just within the Close


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

, three of which are short while the fourth is very long and bundled with the long spines of other cells in the chain. The bundles of long spines from various chains come together in the centre of the colony. One plate-like chloroplast is present per cell and is located in the girdle zone (Cupp 1943). Cells are yellow-brown in colour.
Resting spores are smooth and centrally located (Cupp 1943).


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): 2 - 15 μm
Small diameter Close

Transapical axis

In diatoms, the longitudinal axis of the valve.

(transapical axis
): 2 - 10 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
): 2 - 12 μm
(Kraberg et al. 2010)

Similar species


Harmful effects

May cause physical damage (Kraberg et al. 2010).


Neritic (Cupp 1943). Very common in benthic communities (Booth et al. 2002).


Cosmopolitan (Hasle and Syvertsen 1997), with higher densities in colder waters (Kraberg et al. 2010).
Most abundant in March in northern and Arctic waters (Donnelly 2006). Present from spring to fall, being very abundant in spring in Northern European seas (Kraberg et al. 2010). An important contributor to spring blooms in NE Atlantic and in Artic waters (Degerlund and Eilertsen 2010). Forms blooms in late summer in northern Canadian waters (Booth et al. 2002).
One of the dominant species in late spring in Saanich Inlet, BC (Sancetta and Calvert 1988). Most abundant in early spring and summer off California (Cupp 1943).

Growth conditions

Occurs in the Close


The zone near the surface of the water where the light intensity is sufficient to support net photosynthesis (Letelier et al. 2004). Defined as the area above "the depth at which the photon flux equals 1% of the flux measured just above the air-sea interface" (Ryther 1956).

zone during low Close


Various chemical substances that an organism needs for metabolism (i.e., to live and grow). These are usually taken up from the environment. Some examples include nitrate, phosphate, silica (for diatoms), iron, copper, etc. Some nutrients, like copper, are required for growth, but can also be toxic at high levels.

conditions, and sinking deeper when nutrients are abundant (Booth et al. 2002). Sensitive to low salinities; usually occurs at salinities of 24 - 34 (Shevchenko et al. 2008). Optimal N:P ratio of 16:1 (Li et al. 1990).
Has high iron uptake and storage capacity, and may be able to withstand high concentrations of iron. The maximum to minimum iron Close


(as in, cell quota for a nutrient) The amount of a macro- or micronutrient required by an organism to fulfill its life cycle.

ratio was found to be 3.4 to 4.2 (Iwade et al. 2006).
Resting spores are formed under low nitrate conditions, accumulate in fecal pellets and then are released when conditions are favourable (Booth et al. 2002).

Environmental Ranges

Depth range (m): 0 - 292
Temperature range (°C): -1.952 - 29.468
Nitrate (μmol L-1): 0.056 - 31.807
Salinity: 18.564 - 37.775
Oxygen (mL L-1): 4.500 - 9.192
Phosphate (μmol L-1): 0.048 - 2.190

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 - 66.097
(OBIS 2012, cited in EOL 2012)

Bloom characteristics

Information not available.


Booth, B. C., Larouche, P., Bélanger, S., Klein, B., Amiel, D. and Mei, Z. P. 2002. Dynamics of Chaetoceros socialis blooms in the North Water. Deep-Sea Research II. 49: 5003-5025.

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

Degerlund, M. and Eilertsen, H. C. 2010. Main species characteristics of phytoplankton spring blooms in NE Atlantic and Arctic waters (68 - 80° N). Estuaries and Coasts. 33: 242-269.

Donnelly, K. A. M. 2006. The importance of morphological/physiological heterogeneity as adaptive strategies in stocks of common Northern/Arctic phytoplankton species with special focus on the common diatom Chaetoceros socialis. Master's Thesis, University of Tromsø, Norway.

Encyclopedia of Life (EOL). 2012. Chaetoceros socialis. Accessed 31 Mar 2012.

Guiry, M. D. 2012. Chaetoceros socialis H. S. Lauder, 1864. Accessed 31 Mar 2012.

Guiry, M. D. and Guiry, G. M. 2012. Chaetoceros socialis H. S. Lauder. Accessed 31 Mar 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.

Iwade, S., Kuma, K., Isoda, Y., Yoshida, M., Kudo, I., Nishioka, J. and Suziki, K. 2006. Effect of high iron concentrations on iron uptake and growth of a coastal diatom Chaetoceros sociale. Aquatic Microbial Ecology. 43: 177-191.

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

Li, W., Li, S. and Wang, X. 1990. Effects of phosphate on the photosynthetic rate of Chaetoceros socialis. Tropic Oceanology/Redai Haiyang. 9(2): 58-62.

Ocean Biogeographic Information System (OBIS). 2012. Chaetoceros socialis. Accessed 31 Mar 2012.

Shevchenko, O. G., Orlova, T. Y. and Aizdaicher, N. A. 2008. Development of the diatom Chaetoceros socialis f. radians (Schütt) Proschkina-Lavrenko 1963 in laboratory culture. Russian Journal of Marine Biology. 34(4): 224-229.

Sancetta, C. and Calvert, S. E. 1988. The annual cycle of sedimentation in Saanich inlet, British Columbia: implications for the interpretation of diatom fossil assemblages. Deep Sea Research Part A. Oceanographic Research Papers. 35(1): 71-90.

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