Rhizosolenia setigera

General Close


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

Shape Cylindrical
Size Length 100 - 500 μm, width 4 - 20 μm
Colour Yellow-brown
Connection None (solitary)
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.

Many small elliptical 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.


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.

Shallow water 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).

Harmful effects Produces toxins and causes Close


Describing a condition where there is no available oxygen for primary production. Oxygen may be present in complexed forms that are not available for phytoplankton. A related term is hypoxia, where oxygen is present at very low concentrations.

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).

, Close


Of or relating to estuaries.

and oceanic
Geographic Close


Widely distributed; occurring in many parts in the world.

except in polar waters
Seasonal Late spring to 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).

24 - 36
Temperature -2 - 30 °C


Rhizosolenia japonica Castracane 1886
Rhizosolenia hensenii Schuett 1900
Pyxilla baltica Grunow 1881
Rhizosolenia pungens Cleve-Euler 1937
Rhizosolenia crassispina Schroeder
(EOL 2011)


Empire Eukaryota
Kingdom Chromista
Subkingdom Harosa
Infrakingdom Heterokonta
Phylum Ochrophyta
Class Coscinodiscophyceae
Subclass Rhizosoleniophycidae
Order Rhizosoleniales
Family Rhizosoleniaceae
Genus Rhizosolenia
Species R. setigera Brightwell 1858

(Guiry and Guiry 2011)


Rhizosolenia setigera is an Close


An organism that can use inorganic materials for primary production of complex organic compounds by practicing photosynthesis or chemosynthesis. For example, plants are autotrophic organisms.

centric diatom (Smithsonian 2012). It has both sexual and asexual cycles of reproduction (Guiry and Guiry 2011). R. setigera produces 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
, which are completely different from the mother cell (Horner 2002). Resting pores are torpedo-shaped and are formed in pairs (Smithsonian 2012).


Cells are cylindrical, with conical Close


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

narrowing into a long, straight and needle-like Close


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

(Horner 2002, LUMCON 2012). Cells are much longer than they are wide and valves do not have Close


(plural: otaria) In Rhizosolenia and related diatoms, an elongated, membranous thickening of the cell wall near the base of an external process. Otaria were previously called "wings" and can be seen as small lobes at the base of the needle-like spine at each end of a Rhizosolenia cell (Hasle and Syvertsen 1996).

(EOL 2011). Cell frustule is weakly Close


Describing the character (i.e., white, shimmery) or chemical presence silicon dioxide (SiO2) as a component of phytoplankton cell covering.

. R. setigera cells are wider in the centre and gently narrow towards either end (Hasle and Syvertsen 1996). Cell has many chloroplasts located through out the cell (Smithsonian 2012). Cells are often solitary (Horner 2002).


Length: 100 - 500 μm
Diameter: 2 - 50 μm
(Horner 2002)

Similar species

Rhizosolenia pungens is believed to be a variety of R. setigera. The R. setigera cell gradually narrows into a needle-like spine (Smithsonian 2012). R. pungens abruptly narrows into a spine (Smithsonian 2012). R. setigera produces resting spores, but R. pungens does not (Smithsonian 2012).

Harmful effects

Produces chemicals (monocyclic alkenes) that might cause mortalities of marine organisms due to oxygen depletion during bloom decay (EOL 2011).


Mainly coastal and estuarine, though occasionally found in open oceans (EOL 2011).


R. setigera is Close


Describing organisms that are able to withstand a wide range of temperatures in the environment.

(found in temperatures ranging from -2 - 30 °C) and Close


Describing organisms that are able to withstand a wide range of salinities in the environment (e.g., fresh, brackish, salt).

(found in salinity ranging from 1.5 - 37; EOL 2011). It is considered to be a north temperate species but has been seen throughout the world's oceans from tropical to cold temperate waters (Smithsonian 2012). R. setigera is not found in polar waters (EOL 2011).

Environmental Ranges

Depth range (m): 0 - 270
Temperature range (°C): -1.765 - 29.468
Nitrate (μmol L-1): 0.053 - 15.539
Salinity: 24.029 - 35.840
Oxygen (mL L-1): 4.444 - 9.192
Phosphate (μmol L-1): 0.046 - 1.696

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): 0.648 - 37.729
(EOL 2011)

Bloom characteristics

Blooms in shallow water embayments in late spring and early fall (Haigh 2010, Horner 2002).


Encyclopedia of Life (EOL). 2011. Rhizosolenia setigera Brightwell 1858. http://www.eol.org. Accessed 11 Sept 2011.

Guiry, M. D. and Guiry, G. M. 2011. Rhizosolenia setigera Brightwell 1858. http://www.algaebase.org. Accessed 09 Sept 2011.

Haigh, N. 2010. Harmful Plankton Handbook. Nanaimo, BC. Canada. 53.

Hasle, G. R. and Syvertsen, E. E. 1996. Marine Diatoms. Tomas, C. R. (ed.) Identifying Marine Phytoplankton. Academic Press, Inc., San Diego, 531.

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

Louisiana University Marine Consortium (LUMCON). 2012. Rhizosolenia setigera Brightwell 1858. http://phytoplanktonguide.lumcon.edu/display.asp?dtype=organism&id=258. Accessed 21 Jan 2012.

Smithsonian Institution. 2012. Rhizosolenia setigera Brightwell 1858. http://www.sms.si.edu/irlspec/Rhizos_setige.htm. Accessed 21 Jan 2012.

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