Eunotia bilunaris

(Ehrenb.) Schaarschm. 1881      Category: Eunotioid
BASIONYM: Synedra bilunaris Ehrenb. 1832
SYNONYM(S): Eunotia bilunaris (Ehrenb.) M.G.M.Souza in M.G.M.Souza and Moreira-FIlho 1999 

Eunotia bilii


Eunotia boomsma

LM scalebar = 10 µm = 40 pixels.


Contributor: David R.L. Burge | Mark Edlund - April 2015
Length Range: 33-110 µm
Width Range: 3.1–4.7 µm
Striae in 10 µm: 11–16 at center of the valve, 15–19 near the apices


Valves are arcuate, with convex dorsal and concave ventral margins. Margins are parallel near the apices. In some specimens, the ventral margins are slightly swollen near the transapical axis. Apices are rounded in larger specimens, becoming more acute in smaller speciments. Helictoglossae are positioned near the apices, along the ventral margin. The distal raphe end curves from the ventral margin onto the valve face and then back towards the center of the valve. Striae are spaced evenly, becoming more dense near the apices. Areolae are fine and not visible in LM.

Original Description

Basionym: Synedra bilunaris
Author: Ehrenb. 1832
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Burge, D., and Edlund, M. (2015). Eunotia bilunaris. In Diatoms of the United States. Retrieved April 19, 2018, from

Species: Eunotia bilunaris

Contributor: David R.L. Burge | Mark Edlund

Reviewer: Paula Furey


Alles, E., Nörpel-Schempp, M. and Lange-Bertalot, H. (1991). Taxonomy and ecology of characteristic Eunotia species in headwaters with low electric conductivity. Nova Hedwigia 53: 171-213.

Antoniades, D., Hamilton, P.B., Douglas, M.S.V. and Smol, J.P. (2008). Diatoms of North America: The freshwater floras of Prince Petrcik, Ellef Ringnes and northern Ellesmere Islands from the Canadian Arctic Archipelago. Iconographia Diatomologica 17.

Burge, D.R.L. (2014). Relations of water quality, land use buffers, and diatom communities of connected depressions within the Cache River Watershed, Arkansas, USA. M.S. Thesis. Arkansas State University, Jonesboro, Arkansas. 141 pp.

Ehrenberg, C.G. (1832). Über die Entwickelung und Lebensdauer der Infusionsthiere; nebst ferneren Beiträgen zu einer Vergleichung ihrer organischen Systeme. Abhandlungen der Königlichen Akademie Wissenschaften zu Berlin, Physikalische Klasse 1831: 1-154, pls I-IV.

Fallu, M.-A., Allaire, N. and Peinitz, R. (2000). Freshwater diatoms from northern Québec and Labrador (Canada). Species-environment relationships in lakes of boreal forest, forest-tundra and tundra regions. Bibliotheca Diatomologica 45: 1-200.

Furey, P.C., Lowe, R.L. and Johansen, J.R. (2011). Eunotia Ehrenberg (Bacillariophyta) of the Great Smoky Mountains National Park, USA. Bibliotheca Diatomologica 56: 1-134.

Schaarschmidt, G. (1881). Specimen phycologiae aequatoriensis. Magyar Novenytani Lapok 5(50):17-24.

Siver, P.A. and Hamilton, P.B. (2011). Diatoms of North America: The Freshwater Flora of Waterbodies on the Atlantic Coastal Plain. Iconographia Diatomologica 22.

Siver, P.A., Hamilton, P.B., Stachura-Suchoples, K. and Kociolek, J.P. (2005). Diatoms of North America. The Freshwater Flora of Cape Cod. Iconographia Diatomologica 14: 1-463.

Vanormelingen, P., Cherpurnov, V.A., Mann, D.G., Cousin, S. and Vyverman, W. (2007). Congruence of morphological, reproductive and ITS-rDNA sequence data in some Australasian Eunotia bilunaris (Bacillariophyta) . European Journal of Phycology 42: 61–79.

Zimmermann, C., Poulin, M. and Pienitz, R. (2010). Diatoms of North America: The Pliocene-Pleistocene freshwater flora of Bylot Island, Nunavut, Canadian High Arctic. Iconographia Diatomologica (H. Lange-Bertalot, ed.), Volume 21, A.R.G. Gantner Verlag K.G., Ruggell, 407 pp.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA
Original INA

California Academy of Sciences (CAS)

Eunotia bilunaris CAS

NCBI Genbank Taxonomy

Eunotia bilunaris NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 33185

Autecology Discussion

Eunotia bilunaris has wide geographic and habitat distribution in North America. It has been reported from epiphytic and epilithic site of the Great Smoky Mountains (Furey et al. 2011), wetlands (Burge 2014), lakes (Antoniades et al. 2008, Siver and Hamilton), and in rivers of Québec-Labrador (Fallu et al. 2000).

Antoniades et al. (2008) observed E. bilunaris in less than 2% abundance occurring benthic in small lakes and ponds of Prince Patrick Island (Northwest Territories, Canada), with the following water chemistry: pH 7.1-8.0, conductivity 40-97 µS/cm, and 4.79-10.34 DOC (mg/L). Siver and Hamilton (2011) observed E. bilunaris occurring in ponds and canals of the Pocosin NWR (North Carolina), with a pH 4.5+/-1.2 and TP 37+/-18 µg/L. Burge (2014) observed E. bilunaris populations occurring <1% to 48% relative abundance in assemblages with E. formica, E. metamonodon, E. praeruptua, as well as species of Gomphonema, Navicula, and Pinnularia, in cypress-tupelo wetlands of the Cache River NWR (Arkansas) with the following water chemistry: 19.2–31.5oC, pH 5.18 –7.7, DO 0.1–7.7 mg/L, specific conductance 11.8–1358 µS/cm, Turbidity 3.9–628 NTU, Chlorophyll-a 0–167.3mg/L, NH3-N 0.1–16.1, NO3-N <0.1–0.8 mg/L, NO2-N 0–0.2 mg/L, TN 0.6–8.1 mg/L, TP <0.1–4.6 mg/L, and PO4-P <0.1–2.8 mg/L.

In Europe, E. bilunaris is found within moderately dystrophic waters with increased concentrations of sulfate (Alles et al. 1991).

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

Eunotia bilunaris

EMAP Response Plots

Eunotia bilunaris

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.