Thalassiosira pseudonana (Hustedt) Hasle and Heimdal, (1957) 1970

Common Name: A centric diatom

Synonyms and Other Names:

Cyclotella nana

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Identification: This diatom can occur singly or in chains up to 6 cells long. It typically exhibits a ring of fultoportulae around the edge of the valve face, costae that may run from the middle of the valve face to its edges, and one labiate process. The central region of the valve face is often bounded by an irregular siliceous ring and may or may not exhibit central fultoportulae. The valve face is often striated radially and hexagonal to polygonal areolae are often apparent in the central region (Belcher and Swale 1977, 1986, Harris et al. 1995, Hasle 1976, Lange et al. 1983, Lowe and Busch 1975, Muylaert and Sabbe 1996, Sabater and Klee 1990).

Thalassiosira pseudonana can range in diameter from 2.5–15 µm (Belcher and Swale 1977, 1986, Harris et al. 1995, Hasle 1976, Lange et al. 1983, Lowe and Busch 1975, Muylaert and Sabbe 1996, Price et al. 1987).

Size: 2.5 to 15 microns

Native Range: Unclear. Thalassiosira pseudonana is considered widespread. It is known from freshwater habitats in Europe and the former USSR, brackish and coastal waters of Europe, coastal waters of Japan, coastal waters of Australia, coastal waters of India, the Argentine Sea, the Baltic Sea, coastal waters on both sides of North America, and a few inland habitats in North America (Ake-Castillo et al. 1999, Belcher and Swale 1977, 1986, Blinn et al. 1981, Genkal and Prokina 1981, Harris et al. 1995, Hasle 1978, Kiss 1984, 1996, Lange et al. 1983, Lowe and Busch 1975, Mills et al. 1993, Muylaert and Sabbe 1996, Raman and Prakash 1989).

Map Key
This map only depicts Great Lakes introductions.

Great Lakes Nonindigenous Occurrences: Thalassiosira pseudonana was recorded for the first time in the Lake Erie drainage in an Ohio artesian well in 1973, but it may have been present at an earlier date elsewhere in the Great Lakes drainage. It was later recorded from Lake Erie, Lake Ontario, Lake Michigan, and the Sandusky River, which flows into Lake Erie (Lowe and Kline 1976, Mills et al. 1993).

Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Thalassiosira pseudonana are found here.

State/ProvinceYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
New York199319931Lake Ontario
Ohio197319932Lake Erie; Sandusky

Table last updated 10/16/2019

† Populations may not be currently present.

* HUCs are not listed for areas where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).

Ecology: Thalassiosira pseudonana is a cosmopolitan species typically found in freshwater and coastal brackish habitats. It is usually a phytoplankton species but has also been recorded in the periphyton. It is eurythermal, experiencing good growth from 10–30°C, with an optimum around 21°C. Growth rates typically increase with increasing temperature, which confers T. pseudonana a competitive advantage at higher temperatures. Maximum abundance has been recorded in different regions of the world in late spring, summer, and late fall (Ferguson et al. 1976, Goldman and Ryther 1976, Harris et al. 1995, Hegseth and Saksaug 1983, Lowe and Busch 1975, Lowe and Kline 1976). The distribution and growth of T. pseudonana is primarily regulated by water temperature and day length (Brand et al. 1981, Ferguson et al. 1976, Hegseth and Skashaug 1983).

Thalassiosira pseudonana, like many diatom species, is capable of sexual reproduction. In general, the rate of reproduction increases with increasing temperature. It has a dormant stage that is most likely a physiological resting cell (Armbrust et al. 2001, Brand et al. 1981, McQuoid 2005). Growth can be limited by changes in concentrations of vitamin B-12, silicon, selenium, zinc, nitrogen, phosphorus, or other vitamins (Guillard et al. 1973, Maestrini et al. 1997, Miao and Wang 2006, Price et al. 1987, Swift and Taylor 1974, Sunda and Huntsman 1992, 2005).

Although non-toxic itself, this species is often associated with relatively polluted regions, places where chemical oxygen demand is elevated and nutrient concentrations are very high, and waters experiencing red tides (de Almeida and Gil 2001, Gao et al. 2006, Mallin et al. 1995, Raman and Prakash 1989, Weckstrom and Juggins 2006). Thalassiosira pseudonana grows well at pH of 7–8.8, but its growth rates are reduced at higher pH because CO2 becomes limiting (Chen and Durbin 1994). It is capable of quickly adapting to changes in irradiance by adjusting cell volume (Thompson et al. 1991).

Means of Introduction: Thalassiosira pseudonana was very likely introduced in ballast water to the Great Lakes basin. It was first discovered in an artesian well but was probably originally introduced elsewhere in the basin at a location more easily accessible to ships carrying ballast water (Mills et al. 1993).

Status: Established where recorded.

Great Lakes Impacts:

There is little or no evidence to support that Thalassiosira pseudonana has significant environmental impacts in the Great Lakes.

Thalassiosira pseudonana has been found in the Great Lakes basin composing 31% of the periphyton community and 90% of the plankton community (Lowe and Busch 1975). McQuoid (2005) reported growth of T. pseudonana after 2 years in storage, indicating the presence of a dormant state that seems to be triggered by temperature and light cues. This dormant state could give T. pseudonana a competitive advantage over native species, but this has not been specifically researched.

There is little or no evidence to support that Thalassiosira pseudonana has significant socio-economic impacts in the Great Lakes.

There is little or no evidence to support that Thalassiosira pseudonana beneficial effect in the Great Lakes.
Thalassiosira pseudonana was found to be useful for mariculture because it has a high fatty-acid composition (Volkman et al. 1989). Thalassiosira pseudonana is also used as a model organism for silica biomineralization because its entire gene sequenced has been published. Biomineralizaton is a growing field that is using diatoms to accelerate silica formation and form macromolecular assemblies that might act as structure-directing templates (Sumper and Brunner 2008).


Regulations (pertaining to the Great Lakes region)
There are no known regulations for this species.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

There are no known biological control methods for this species.

There are no known physical control methods for this species.

There are no known chemical control methods for this species.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

Remarks: In 1958, Guillard isolated three diatom clones from an estuarine habitat (3-H), slope water (7-15), and open ocean (13-1). These clones were considered for years to be different forms of T. pseudonana. However, it turns out that clone 7-15 is identical to T. guillardii from brackish water and clone 13-1 is another species. Only clone 3-H is still considered to be T. pseudonana (Hasle 1982).

References: (click for full references)

Ake-Castillo, J.A., D.U. Hernandez-Becerril, and M.E. Meave del Castillo. 1999. Species of the genus Thalassiosira (Bacillariophyceae) from the Gulf of Tehuantepec, Mexico. Botanica Marina 42(6): 487-503.

de Almeida, S.F.P., and M.C.P. Gil. 2001. Ecology of freshwater diatoms from the central region of Portugal. Cryptogami Algologie 22(1): 109-126.

Armbrust, E.V., and H.M. Galindo. 2001. Rapid evolution of a sexual reproduction gene in centric diatoms of the genus Thalassiosira. Applied and Environmental Microbiology 67(8): 3501-3513.

Belcher, J.H., and E.M.F. Swale. 1977. Species of Thalassiosira diatoms (Bacillariophyceae) in the plankton of English rivers. British Phycological Journal 12(3): 291-296.

Belcher, J.H., and E.M.F. Swale. 1986. Notes on some small Thalassiosira species (Bacillariophyceae) from the plankton of the lower Thames and other British estuaries identified by transmission electron microscopy. British Phycological Journal 21(2): 139-146.

Blinn, D.W., M. Hurley, and L. Brokaw. 1981. The effect of saline seeps and restricted light on the seasonal dynamics of phyto plankton communities within a southwestern USA desert canyon stream. Archiv für Hydrobiologie 92(3): 287-305.

Brand, L.E., L.S. Murphy, R.R.L. Guillard, and H.T. Lee. 1981. Genetic variability and differentiation in the temperature niche component of the diatom Thalassiosira pseudonana. Marine Biology (Berlin) 62(2-3): 103-110.

Chen, C.Y., and E.G. Durbin. 1994. Effects of pH on the growth and carbon uptake of marine phytoplankton. Marine Ecology Progress Series 109(1): 83-94.

Ferguson, R.L., A. Collier, and D.A. Meeter. 1976. Growth response of Thalassiosira pseudonana clone 3H to illumination temperature and nitrogen source. Chesapeake Science 17(3):1 48-158.

Gao, H., Y. Gao, and J. Liang. 2006. Xiamen Daxue Xuebao (Ziran Kexue Ban) 45(4): 553-557.

Genkal, S.I., and N.Y. Prokina. 1981. Massive development of a little known diatom Thalassiosira pseudonana in the Volga Russian-SFSR USSR. Gidrobiologicheskii Zhurnal 17(1): 42-44.

Goldman, J.C., and J.H. Ryther. 1976. Temperature-influenced species composition in mass cultures of marine phytoplankton. Biotechnology and Bioengineering XVIII: 1125-1144.

Guillard, R.R.L., P. Kilharn, and T.A. Jackson. 1973. Kinetics of silicon-limited growth in the marine diatom Thalassiosira pseudonana Hasle and Heimdal (Cyclotella nana Hustedt). Journal of Phycology 9(3): 233-237.

Harris, A.S.D., L.K. Medlin, J.Lewis, and K.J. Jones. 1995. Thalassiosira species (Bacillariophyceae) from a Scottish sea-loch. European Journal of Phycology 30: 117-131.

Hasle, G.R. 1976. Examination of diatom type material Nitzschia delicatissima, Thalassiosira minuscula, and Cyclotella nana. British Phycological Journal 11(2): 101-110.

Hasle, G.R. 1978. Some fresh water and brackish water species of the diatom genus Thalassiosira. Phycologia 17(3): 263-292.

Hasle, G.R. 1982. The morphology of the Guillard clones 3-H, 7-15 and 13-1 clones. British Phycological Journal 17(2): 233.

Hegseth, E.N., and E. Sakshaug. 1983. Seasonal variation in light- and temperature-dependent growth of marine planktonic diatoms in in situ dialysis cultures in the Trondheimsfjord, Norway (63ºN). Journal of Experimental Marine Biology and Ecology 67: 199-220.

Kiss, K.T. 1984. Occurrence of Thalassiosira pseudonana new record Bacillariophyceae in some rivers of Hungary. Acta Botanica Hungarica 30(3-4): 277-288.

Kiss, K.T. 1996. Diurnal changes of planktonic diatoms in the River Danube near Budapest (Hungary). Archiv für Hydrobiologie Supplement 112: 113-122.

Lange, C., R.M. Negri, and H.R. Benavides. 1983. Some species of the genus Thalassiosira Bacillariophyceae of the Argentine Sea 1. Iheringia Serie Botanica 31: 9-30. (in Spanish)

Lowe, R.L., and D.E. Busch. 1975. Morphological observations on two species of the diatom genus Thalassiosira from fresh-water habitats in Ohio. Transactions of the American Microscopical Society 94(1): 118-123.

Lowe, R.L., and P.A. Kline. 1976. Planktonic centric diatoms from the Sandusky River, Ohio, USA. Pp. 143-152 in D. B. Baker, W.B. Jackson, and B.L. Prater (eds.) International Reference Group on Great Lakes Pollution from Land Use Activities. Sandusky River Basin Symposium, Tiffin, Ohio, USA, May 2-3, 1975. US Government Printing Office:Washington, D.C. 475 pp.

Maestrini, S.Y., B.R. Berland, M. Breret, C. Bechemin, R. Poletti, and A. Rinaldi. 1997. Nutrients limiting the algal growth potential (AGP) in the Po River plume and an adjacent area, northwest Adriatic Sea: enrichment bioassays with the test algae Nitzschia closterium and Thalassiosira pseudonana. Estuaries 20(2): 416-429.

Mallin, M.A., J.M. Burkholder, M.L. Larsen, and H.B. Glasgow Jr. 1995. Response of two zooplankton grazers to an ichthyotoxic estuarine dinoflagellate. Journal of Plankton Research 17(2): 351-363.

McQuoid, M.R. 2005. Influence of salinity on seasonal germination of resting stages and composition of microplankton on the Swedish west coast. Marine Ecology Progress Series 289: 151-163.

Miao, A.J., and W.X. Wang. 2006. Fulfilling iron requirements of a coastal diatom under different temperatures and irradiances. Limnology and Oceanography 51(2): 925-935.

Mills, E.L., J.H. Leach, J.T. Carlton, and C.L. Secor. 1993. Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions. Journal of Great Lakes Research 19(1): 1-54.

Muylaert, K., and K. Sabbe. 1996. The diatom genus Thalassiosira (Bacillariophyta) in the estuaries of the Schelde (Belgium/The Netherlands) and the Elbe (Germany). Botanica Marina 39(2): 103-115.

Price, N.M., P.A. Thompson, and P.J. Harrison. 1987. Selenium: an essential element for growth of the coastal marine diatom Thalassiosira pseudonana (Bacillariophyceae). Journal of Phycology 23: 1-9.

Raman, A.V., and K.P. Prakash. 1989. Phytoplankton ecology in relation to pollution in Visakhapatnam Harbour, east coast of India. Asian Marine Biology 6: 161-166.

Sabater, S., and R. Klee. 1990. Observations on centric diatoms of the River Ebro, Spain: phytoplankton, with special interest on some small Cyclotella. Diatom Research 5(1): 141-154.

Sumper, M., and E. Brunner. 2008. Silica biominerialisation in diatoms: the model organism Thalassiosira pseudonana. ChemBioChem 9: 1187-1194.

Sunda, W. G. and S. A. Huntsman. 1992. Feedback interactions between zinc and phytoplankton in seawater. Limnology and Oceanography 37(1):25-40.

Sunda, W.G., and S.A. Huntsman. 2005. Effect of CO2 supply and demand on zinc uptake and growth limitation in a coastal diatom. Limnology and Oceanography 50(4): 1181-1192.

Swift D.G., and W.R. Taylor. 1974. Growth of vitamin B12-limited cultures: Thalassiosira pseudonana, Monochrysis lutheri, and Isochrysis galbana. Journal of Phycology 10: 385-391.

Thompson, P.A., P.J. Harrison, and J.S. Parslow. 1991. Influence of irradiance on cell volume and carbon quota for ten species of marine phytoplankton. Journal of Phycology 27(3): 351-360.

Volkman, J.K., S.W. Jeffery, P.D. Nichols, G.I. Rogers, and C.D. Garland. 1989. Fatty acid and lipid composition of 10 species of microalgae used in mariculture. Journal of Experimental Marine Biology and Ecology 128(3): 219-240.

Weckstrom, K., and S. Juggins. 2006. Coastal diatom-environment relationships from the Gulf of Finland, Baltic Sea. Journal of Phycology 42(1): 21-35.

Other Resources:
Author: Kipp, R.M., M. McCarthy, and A. Fusaro

Contributing Agencies:

Revision Date: 9/12/2019

Citation for this information:
Kipp, R.M., M. McCarthy, and A. Fusaro, 2020, Thalassiosira pseudonana (Hustedt) Hasle and Heimdal, (1957) 1970: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI,, Revision Date: 9/12/2019, Access Date: 10/1/2020

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.