Alexandrium tamarense

General Dinoflagellate
Shape Spherical
Size Length 22 - 51 μm, width 17 - 44 μm
Colour Orange-brown
Connection None (solitary)
Covering Cellulose Close


(plural: thecae) Cell wall. In dinoflagellates, it is composed of cellulose plates within vesicles (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.

Orange-brown chloroplasts
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

Binary fission

A form of asexual reproduction where one cell divides into two identical cells. All prokaryotes and some eukaryotes reproduce in this manner. Compare with mitosis, where the nucleus must also divide, adding an extra step to the process.

(binary fission


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.

Blooms in restricted Close


"Enclosed areas along the shoreline where freshwater from groundwater and streams is mixed with salt water from the surrounding oceans" (McCaffery and Livingston 2000).

and salty coastal and Close


Of or relating to estuaries.

Harmful effects Associated with toxic paralytic shellfish poisoning Close

Paralytic Shellfish Poison

(PSP) Results from human consumption of filter-feeding shellfish that have fed on toxic saxitoxin-producing dinoflagellates. During certain phytoplankton blooms, shellfish can accumulate and bio-concentrate the toxins. The main species associated with PSP in Canada are dinoflagellates in the genus Alexandrium. "Symptoms of PSP begin with a tingling sensation or numbness around the lips within 5 - 30 minutes of ingestion, gradually spreading to the face and neck. With moderate to severe intoxication, symptoms include incoherent speech, stiffness and non-coordination of limbs and slight respiratory difficulty. Gastrointestinal symptoms of nausea, vomiting, diarrhea and abdominal pain are less common. Following high intake, paralysis of respiratory muscles may progress to respiratory arrest and death within 2 - 12 hours after consumption" (DFO 2010).

Habitat Cold coastal, estuarine waters and restricted embayments
Geographic Cold temperate waters of North America, Europe and Japan
Seasonal Summer (mostly July - August)
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).

20.8 - 29.5
Temperature -2 - 28 °C


Gonyaulax tamarensis Lebour 1925
Gonyaulax exccavata (Braarud) Balech 1971
Gonyaulax tamarensis var. excavate Braarud 1945
Gessnerium tamarensis (Lebour) Loeblich and Loeblich 1979
Protogonyaulax tamarensis (Lebour) Taylor 1979
Protogonyaulax excavate (Braarud) Taylor 1979
Alexandrium excavatum (Braarud) Balech and Tagen 1985
(Smithsonian 2011, Kraberg et al. 2010)


Empire Eukaryota
Kingdom Protozoa
Subkingdom Biciliata
Infrakingdom Alveolata
Phylum Dinoflagellata
Class Dinophyceae
Subclass Peridniphycidae
Order Gonyaulacales
Family Gonyaulacaceae
Genus Alexandrium
Species A. tamarense (Lebour) E. Balech 1985

(Guiry and Guiry 2011)


Alexandirum tamarense is a photosynthetic dinoflagellate. It has a number of orange-brown chloroplasts. It reproduces asexually by binary fission, although it can also reproduce sexually through joining of dissimilar Close


A reproductive cell (sperm or ovum) that can combine with another reproductive cell to create a new individual.



Sexual reproduction involving two dissimilar gametes, e.g. sperm and egg.

; Smithsonian 2011). It produces oval resting Close


"A thick-walled dormant cell" (Horner 2002).

with smooth wall. Its resting cysts contain reddish lipids and are covered with mucus (Kraberg et al. 2010).


Alexandrium tamarense cells are relatively small. Cell size can range from 22 - 51 μm, with cells almost as wide as they are long (EOL 2011). Cells are spherical and have Close


In thecate dinoflagellates, the anterior part of a dinokont cell above the cingulum. The equivalent of epicone for naked dinoflagellates.

and Close


In thecate dinoflagellates, the posterior part of a dinokont cell above the cingulum. The equivalent of a hypocone for naked dinoflagellates.

that are nearly equal in size (Smithsonian 2011).


Length: 22 - 51 μm
Width: 17 - 44 μm

Similar species

Alexandrium tamarense is similar to A. catenella but A. catenella does not have a Close


Relating to the underside of an organism; abdominal.

pore which may be difficult to see (Smithsonian 2011). Also, A. catenella can form chains of 2-16 cells while A. tamarense is solitary.

Harmful effects

Alexandrium tamarense causes paralytic shellfish poisoning (PSP). This is a potent neurotoxin, which can block sodium channels within cells, inhibiting transmission of nerve impulses (Armi et al. 2011). This toxin is observed to accumulate in shellfish (Armi et al. 2011) and can accumulate up the food chain killing fish, seabirds, affecting human health and causing economic loss (Smithsonian 2011). PSP toxins caused several massive fish kills (Atlantic herring, rainbow trout and salmon) resulting from fish feeding on zooplankton that had accumulated large amounts of PSP toxins (Smithsonian 2011). Resting cysts can harbor toxins and are even thought to contain more toxins (10x) than the motile stage (Smithsonian 2011). There are also strains of Alexandrium tamarense that are not harmful (Horner 2002). For example, all known strains in the southern North Sea are non-toxic (Kraberg et al. 2010).


Coastal and estuarine. (Horner 2002).


Alexandrium tamarense is mostly found in coastal cold temperate waters of North America, Europe and Japan (Smithsonian 2011). It is broadly distributed in the North Atlantic and southern North Sea (Kraberg et al. 2010). It has also been reported in warm Mediterranean waters off northern Africa (Armi et al. 2011). Non-toxic strains of Alexandrium tamarense have been reported in Australia and the Gulf of Thailand (Smithsonian 2011).
Summer (July to August).

Growth conditions

A study conducted by Amri et al. (2011) in Lake Tunis in North Africa recorded the highest Alexandrium tamarense cell concentration in the summer (above 29 °C). Alexandrium tamarense can adapt to a wide range of nitrate concentrations. A. tamarense can survive in salinities between 21 - 30, however, high cell growth is observed only when salinity is < 24 (Fauchot et al. 2005). In the Bay of Fundy, Canada, sea surface temperatures above 10 °C encouraged growth of Alexandrium tamarense populations (Medcof 1985).

Environmental Ranges

Depth range (m): 0 - 175
Temperature range (°C): -1.770 - 27.590
Nitrate (μmol L-1): 0.275 - 4.405
Salinity: 21.680 - 30
Oxygen (mL L-1): 4.600 - 8.712
Phosphate (μmol L-1): 0.071 - 1.153

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): 0.927 - 14.986

Bloom characteristics

Localized blooms of Alexandrium tamarense occur in brackish, shallow and restricted embayments and lagoons. Widespread blooms occur in open salty coastal waters and large estuaries (Anderson 1998).


Anderson, D. M. 1998. Physiology and Bloom Dynamics of Toxic Alexandrium Species, with Emphasis on Life Transitions. Physiological Ecology of Harmful Algal Blooms. G: 41.

Armi, Z., Milandri, A., Turki, S., Hajjem, B. 2011. Alexandrium catenella and Alexandrium tamarense in the North Lake of Tunis: bloom characteristics and the occurrence of paralytic shellfish toxin. African Journal of Aquatic Science. 36(1): 47-56.

Encyclopedia of Life (EOL). 2011. Alexandrium tamarense (Lebour) E. Balech 1985. Accessed 05 Nov 2011.

Fauchot, J., Levasseur, M., Roy, S., Gagnon, R. Weise, M. 2005. Environmental Factors Controlling Alexandrium tamarense (Dinophyceae) growth rate during a red tide event in the St. Lawrence estuary (Canada). Phycological Society of America. 41: 263-272.

Guiry, M. D., Guiry, G. M. 2011. Alexandrium tamarense (Lebour) E. Balech 1985. Accessed 05 Nov 2011.

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

Kraberg, A., Baumann, M., Durselen, C. D. 2010. Coastal Phytoplankton Photo Guide for Northern European Seas. Verlag Dr. Friedrich Pfeil, Munchen, Germany.203.

Medcof, J. C. 1985. Life and death with Gonyaulax, an historical perspective. In: Anderson, D. M., White, A. W., Baden, D. G. (eds.) Toxic Dinoflagellates. Elsevier, New York, 1-8.

Smithsonian Institution. 2011. Alexandrium tamarense (Lebour) E. Balech 1985. Accessed 06 Nov 2011.

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