Dactyliosolen fragilissimus

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 40 - 300 μm, diameter 8 - 70 μm
Colour Yellow-brown
Connection Short central spine fitting into depression of adjacent cell
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 plates
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. May have 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 stage


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 clog gills of Close


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

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 Year-round
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 - 38
Temperature -2 - 29 °C


Rhizosolenia fragilissima Bergon 1903 Close


The original name for an organism. In botany, the original published nomenclature from which a new binomial nomenclature is derived for a particular group of organisms (Tindall 1999).

, Close


Expressing the same fundamental type or structure; may or may not be symmetrical (e.g., the two valves of a diatom, where they are the same shape and appearance, but one is bigger than the other). In naming species, a homotypic synonym is one that comes into being when a taxon gets a new name (without being added to an already existing taxon).

(Guiry and Guiry 2011)


Empire Eukaryota
Kingdom Chromista
Subkingdom Harosa
Infrakingdom Heterokonta
Phylum Ochrophyta
Subphylum Khakista
Class Coscinodiscophyceae
Subclass Rhizosoleniophycidae
Order Rhizosoleniales
Family Rhizosoleniaceae
Genus Dactyliosolen
Species D. fragilissimus (Bergon) Hasle 1996

(Guiry and Guiry 2011)


Photosynthetic. Reproduces sexually and asexually (Guiry 2011). May form resting stage cells (Ishii et al. 2009).


Cells are cylindrical, and are loosely united as straight chains. Close


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

ends are rounded and are connected by a short central Close


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

that fits into a depression on the adjacent cell. Chloroplasts are numerous and shaped like small plates. Both the chloroplasts and the Close


(plural: nuclei) In eukaryotic cells, a membrane-bound organelle that contains the cell's genetic information; the nucleus controls the activities of the cell by controlling gene expression.

are near the cell wall (Cupp 1943). Cells are yellow-brown in colour (Guiry 2011).
Cell walls are very thin and weakly Close


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

. Close

Intercalary bands

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

Intercalary bands
are ring or collar-shaped, ending in a straight line (difficult to see with Close


(light microscopy) "Using a microscope in which a beam of light passes through optical lenses to view an image of the specimen" (MCM LTER 2010).

; Cupp 1943, Horner 2002). Rectangular Close


A simple hole through the surface of a diatom valve (Smithsonian 2011).



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

are visible under EM (Hasle and Syvertsen 1997).


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
): 40 - 300 μm
Diameter: 8 - 70 μm
(Kraberg et al. 2010)

Similar species

Guinardia delicatula, which usually has more rectangular ends, and longer Close


At a slanted angle (i.e., not parallel or perpendicular).

(instead of central) spines (Cupp 1943).

Harmful effects

After Close


(settling out) The tendency for particles to settle out of the water column and come to rest at the bottom due to gravitational forces. Factors that influence the rate of sedimentation are particle size, water density and currents.

, blooms can inhibit growth of benthic shellfish by clogging their gills (Lorrain et al. 2000).


Neritic (Cupp 1943).


Cosmopolitan (Kraberg et al. 2010).
Can be found sporadically in coastal waters throughout the year in Northern European seas (Kraberg et al. 2010). Sometimes forms blooms in autumn to early winter around the Baltic Sea (Łotocka 2006) and in early spring and autumn around Florida (Philips et al. 2010).
"North temperate to Close


Relating to the area immediately south of the Arctic.

species. Moderately common off California, but never in large numbers" (Cupp 1943).

Growth conditions

May be favoured during conditions of P deficiency (Carlsson and Graneli 1999), or high (>100) N:P ratios (Hori et al. 1998). Tolerant of Close


Water that is enriched in natural or artificial mineral and organic matter, which promotes an abundance of plant life (i.e., algae), and can result in reduced oxygen conditions.

conditions (Abdalla et al. 1995). May be able to store 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.

and therefore be adapted to living in environments where nutrient availability is variable (Pinckney et al. 1999, Tozzi et al. 2004, Katz et al. 2005, all cited in Philips et al. 2010).
May be more common in areas with intense turbulence, which is needed to keep the larger non-motile diatoms (including D. fragilissimus) 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 (Lauria et al. 1999). Increases in abundance have been observed following Close


A great rise or overflow of a river from heavy rains or spring thaw. In the Strait of Georgia, this usually occurs from March to June. (pers. comm. D. Cassis).

in the fall (Malej 1995). Often appears together with Guinardia delicatula, Leptocylindrus danicus and Cerataulina pelagica (Hasle and Syvertsen 1997).

Environmental Ranges

Depth range (m): 0 - 305
Temperature range (°C): -1.845 - 29.468
Nitrate (μmol L-1): 0.053 - 28.280
Salinity (PSU): 29.401 - 38.049
Oxygen (mL L-1): 4.444 - 8.768
Phosphate (μmol L-1): 0.046 - 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): 0.733 - 59.039
(OBIS 2011, cited in EOL 2011)

Bloom characteristics

Information not available.


Abdalla, R. R., Zaghloul, F. A. and Hussein, N. R. 1995. A statistical modelling of phytoplankton eutrophication in the Eastern Harbour, Alexandria, Egypt. Bulletin of the National Institute of Oceanography and Fisheries (Egypt). 21(1): 125-146.

Carlsson, P. and Graneli, E. 1999. Effects of N:P:Si ratios and zooplankton grazing on phytoplankton communities in the northern Adriatic Sea. II. Phytoplankton species composition. Aquatic Microbial Ecology. 18(1): 55-65.

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). Dactyliosolen fragilissimus (Bergon) G. R. Hasle. http://www.eol.org/pages/908368. Accessed 02 Aug 2011.

Guiry, M. D. 2011. Dactyliosolen fragilissimus (Bergon) Hasle apud G. R. Hasle and Syvertsen, 1996. http://www.marinespecies.org/aphia.php?p=taxdetails&id=149310. Accessed 02 Aug 2011.

Guiry, M. D. and Guiry, G. M. 2011. Dactyliosolen fragilissimus (Bergon) Hasle. http://www.algaebase.org/search/species/detail/?species_id=42283. Accessed 02 Aug 2011.

Hasle, G. R. and Syvertsen, E. E. 1997. Marine diatoms. In: Tomas, C. R. (ed.) Identifying marine Phytoplankon. 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.

Hori, Y., Miyahara, K., Nagai, S., Tsujino, K., Nakajima, M., Yamamoto, K., Yoshida, Y., Araki, N. and Sakai, Y. 1998. Relationships between the dominant phytoplankton and DIN:DIP ratios in Osaka Bay and Harima-Nada. Nippon Suisan Gakkaishi. 64(2): 243-248.

Ishii, K., Ishikawa, A. and Imai, I. 2009. Marine diatoms emerged from in situ surface sediment in a temperate embayment. Phycologia. 48(4, suppl.): 48-48.

Katz, M. E., Finkel, Z. V., Grzebyk, D., Knoll, A. H. and Falkowski, P. G. 2005. Evolutionary trajectories and biogeochemical impacts of marine eukaryotic phytoplankton. Annual Reviews of Ecology and Systematics. 35: 523-556.

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

Lauria, M. L., Purdie, D. A. and Sharples, J. 1999. Contrasting phytoplankton distributions controlled by tidal turbulence in an estuary. Journal of Marine Systems. 21: 189-197.

Lorrain, A., Paulet, Y. M., Chauvaud, L., Savoye, N., Nezan, E. and Guerin, L. 2000. Growth anomalies in Pecten maximus from coastal waters (Bay of Brest, France): relationship with diatom blooms. Journal of Marine Biological Association of the United Kingdom. 80(4): 667-673.

Łotocka, M. 2006. The first observed bloom of the diatom Dactyliosolen fragilissimus (Bergon) Hasle 1996 in the Gulf of Gdańsk. Oceanologia. 48(3): 447-452.

Malej, A., Mozetic, P., Malacic, V., Terzic, S. and Ahel, M. 1995. Phytoplankton responses to freshwater inputs in a small semi-enclosed gulf (Gulf of Trieste, Adriatic Sea). Marine Ecology Progress Series. 120 (1-3): 111-121.

Ocean Biogeographic Information System (OBIS). Dactyliosolen fragilissimus. http://www.iobis.org/mapper/?taxon_id=743787. Accessed 02 Aug 2011.

Philips, E. J., Badylak, S., Christman, M. C. and Lasi, M. A. 2010. Climatic trends and temporal patterns of phytoplankton composition, abundance, and succession in the Indian River Lagoon, Florida, USA. Estuaries and Coasts. 33(2): 498-512.

Pinckney, J. L., Paerl, H. W. and Harrington, M. B. 1999. Responses of the phytoplankton community growth rate to nutrient pulses in variable estuarine environments. Journal of Phycology. 35: 1455-1463.

Tozzi, S., Schofield, O. and Falkowski, P. 2004. Historical climate change and ocean turbulence as selective agents for key phytoplankton functional groups. Marine Ecology Progress Series. 274: 123-132.

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