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Diatoms of the United States is now known as Diatoms of North America.
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Asterionella formosa

Hassall 1850      Category: Araphid

Anomoeoneis fogedii


Asterionella ralfsii var. americana

LM scalebar = 10 µm = 80 pixels.


Contributor: Sarah Spaulding - December 2012
Length Range: 45-68 µm
Width Range: 1.1-4.5 µm
Striae in 10 µm: 24-28


Valves are long and narrow, with capitate apices. Valves are distinctly heteropolar, or may have asymmetric margins, variable within a population. The central sternum is very narrow and may not be distinguishable. The striae are uniseriate and somewhat irregularly spaced. The striae are slightly off-set from one another at the central sternum. Marginal spines may, or may not be present. A single rimoportula is present at the footpole (larger apex). The spines may also be irregularly spaced. In SEM, the spines can be seen to be positioned between the striae. A small apical porefield is present on the margin of the footpole.

Living cells are joined in colonies, linked valve face to valve face, at the footpole by mucilage pads. Asterionella formosa is a common diatom in the plankton of lakes and slow moving rivers.

A rimoportula may be present at either pole, at both poles, or even more than one rimoportula at a pole (Körner 1969, Round et al. 1990). Transmission electron micrographs further show porefields at both apices (Körner 1969). Patrick and Reimer (1966) report maximum valve length of 130 µm in US specimens. Körner (1970) considers A. gracillima to be synonymous with A. formosa. A number of varieties are treated in the same reference by Körner.

Original Description

Author: Hassall 1850
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Spaulding, S. (2012). Asterionella formosa. In Diatoms of the United States. Retrieved May 26, 2018, from

Species: Asterionella formosa

Contributor: Sarah Spaulding

Reviewer: Pat Kociolek


Arnett, H.A., Jasmine E. Saros, J.E. and Mast, M.A. (2012). A caveat regarding diatom-inferred nitrogen concentrations in oligotrophic lakes. Journal of Paleolimnology 47:277–291. 10.1007/s10933-011-9576-z

Hassall, A.H. (1850). The Diatomaceae in the water supplied to the inhabitants of London and the suburban districts. A microscopic examination of the water. London. 60 pp., 6 pls.

Körner, H. (1970). Morphologie und Taxonomie der Diatomeen Gattung Asterionella. Nova Hedwigia 20: 557-724.

Körner, H. (1969). Morphology and Taxonomie der Diatomeengattung Asterionella. Inaugural-Dissertation, der Freien Universität Berlin.

Lund, J.W.G. (1950). Studies on Asterionella formosa Hass. 2. Nutrient depletion and the spring maximum. Journal of Ecology 38: 15-35.

Maberly, S.C., Hurley, M.A., Butterwick, C., Corry, J.E., Heaney, S.I., Irish, A.E., Jaworski, G.H.M., Lund, J.W.G., Reynolds, C.S. and Roscoe, J.V. (1994). The rise and fall of Asterionella formosa in the south basin of Windermere - analysis of a 45 year series of data. Freshwater Biology 31: 19-34.

Mayer, A. (1937). Die Bacillariophyten-Gattungen Fragilaria und Asterionella in Bayern. Ber. Bayerischen Bot. Gesell. 22: 50-85.

McKnight, D., Smith, R.L., Bradbury, J.P., Baron, J. and Spaulding, S.A. (1990). Phytoplankton dynamics in three Rocky Mountain lakes. Arctic and Alpine Research 22: 264-274.

Pappas, J.L. and Stoermer, E.F. (2001). Asterionella Hassall (Heterokontophyta, Bacillariophyceae), taxonomic history and quantitative methods as an aid to valve shape differentiation. Diatom 17:47-58.

Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.

Saros, J.E., Michel, T.J., Interlandi, S.J. and Wolfe, A.P. (2005). Resource requirements of Asterionella formosa and Fragilaria crotonensis in oligotrophic alpine lakes: implications for recent phytoplankton community reorganizations. Canadian Journal of Fisheries and Aquatic Sciences 62: 1681-1681. doi:10.1139/f05-077

Sheibley, R.W., Enache, M., Swarzenski, P.W., Moran, P.W. and Foreman, J.R. (2014). Nitrogen deposition effects on diatom communities in lakes from three national parks in Washington state. Water, Air, and Soil Pollution 225: 1857. 10.1007/s11270-013-1857-x

Spaulding, S.A., Otu, M., Wolfe, A.P. and Baron, J. (2015). Paleolimnological records of nitrogen deposition in shallow, high-elevation lakes of Grand Teton National Park, Wyoming, U.S.A. Arctic, Alpine and Antarctic Research 47(4): 701-715.

Spaulding, S.A., Ward, J.V. and Baron, J. (1993). Winter phytoplankton dynamics in a subalpine lake. Archiv für Hydrobiology 129: 179-198.

Wolfe, A.P., Cooke, C.A. and Hobbs, W.O. (2006). Are current rates of atmospheric nitrogen deposition influencing lakes in the eastern Canadian Arctic?. Arctic, Antarctic, and Alpine Research 38: 465-476.

Wolfe, A.P., Van Gorp, A.C. and Baron, J.S. (2003). Recent ecological and biogeochemical changes in alpine lakes of Rocky Mountain National Park (Colorado, USA): a response to anthropogenic nitrogen deposition. Geobiology 1: 153–168.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Asterionella formosa CAS

NCBI Genbank Taxonomy

Asterionella formosa NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 9001

Autecology Discussion

Asterionella formosa is common in mesotrophic and eutrophic lakes globally and is one of the most common planktonic diatoms in these lakes in the northern hemisphere. Studies of the seasonality of A. formosa date to the classic works of Lund (1950) in Windemere.

In North America, populations of A. formosa, along with Fragilaria crotonensis Kitton, have been shown to increase greatly with increases of reactive nitrogen (Nr) in oligotrophic alpine lakes of the Rocky Mountains. This increase has been interpreted as a response to atmospheric nutrient enrichment (Saros et al. 2005, Saros et al. 2010). Many diatoms in low nutrient lakes respond with population increases even with relatively low loads of reactive nitrogen. In particular, A. formosa has been used as a marker of “critical loads”, defined as the threshold of the nitrogen deposition rate above which there is a discernible ecological effect (Porter and Johnson 2007).

Although A. formosa is common in mesotrophic and eutrophic lakes globally, it has been increasing in presence and abundance in oligotrophic alpine lakes. This increase is interpreted as a response to atmospheric nutrient enrichment. Diatoms respond, even to relatively low loads of anthropogenic reactive nitrogen, in low nutrient lakes. In particular, A. formosa has been a marker of “critical loads”, defined as the threshold of nitrogen deposition rate below which there is no discernible ecological effect (Porter and Johnson 2007). For example, relative abundance of A. formosa in Rocky Mountain National Park lake sediments approaches 60% in some lakes (Wolfe et al. 2003), 20-25% in lakes of the Beartooth Mountains (Saros et al. 2010) and to a lesser extent in shallow lakes of the Tetons (Spaulding et al. 2015). Hoh Lake, in western Washington, increased to more than 20% A. formosa in response to an estimated summer bulk deposition load of 1.0± 0.3 kg N ha-1 yr-1 (Sheibley et al. 2014).


Asterionella lives in colonies, joined by mucilage pads. The elongate shape of the frustules and the spiral colonies are resistant to sinking in their planktonic habitat.

Credit/Source: Image by: Jan Parmentier

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Asterionella formosa

EMAP Response Plots

Asterionella formosa

EMAP citations

Results are published in:

Johnson, T., Hermann, K., Spaulding, S., Beyea, B., Theel, C., Sada, R., Bollman, W., Bowman, J., Larsen, A., Vining, K., Ostermiller, J., Petersen, D. Hargett, E. and Zumberge, J. (2009). An ecological assessment of USEPA Region 8 streams and rivers. U.S. Environmental Protection Agency Region 8 Report, 178 p.

Stoddard, J. L., Peck, D. V., Olsen, A. R., Larsen, D. P., Van Sickle, J., Hawkins, C. P., Hughes, R. M., Whittier, T. R., Lomnicky, G. A., Herlihy, A. T., Kaufman, P. R., Peterson, S. A., Ringold, P. L., Paulsen, S. G., and Blair, R. (2005). Environmental Monitoring and Assessment Program (EMAP) western streams and rivers statistical summary. U.S. Environmental Protection Agency Report 620/R-05/006, 1,762 p.

Stoddard, J. L., Peck, D. V., Paulsen, S. G., Van Sickle, J., Hawkins, C. P., Herlihy, A. T., Hughes, R. M., Kaufman, P. R., Larsen, D. P., Lomnicky, G. A., Olsen, A. R., Peterson, S. A., Ringold, P. L., and Whittier, T. R. (2005). An ecological assessment of western streams and rivers. U.S. Environmental Protection Agency Report 620/R-05/005, 49 p.