Thalassiosira baltica

(Grunow) Ostenf. 1901      Category: Centric
BASIONYM: Cocinodiscus polyacanthus var. baltica Grunow 1880
SYNONYM(S): Cocinodiscus balticus (Grunow) Grunow 

Tetracyclus rupestris


Thalassiosira lacustris

LM scalebar = 10 µm = 80 pixels.


Contributor: David R.L. Burge | Mark Edlund - May 2015
Diameter: 18-27 µm
Rows of areolae in 10 µm:


Valves are disc-shaped, with a flat valve face and broadly curved valve/mantle interface. The areolae are loculate and are organized into radiate, sectored rows. Areolae number 15-18 in 10 µm, at mid-radius. Marginal fultoportulae are organized in two rows, one interior to the other. Close to the margin, the lower row of fultoportulae often appears spine-like. Up to seven central fultoportulae are organized concentrically around the valve center. Three rimoportulae are present on the valve face, closer to the valve margin than to the center of the valve.

Original Description

Basionym: Cocinodiscus polyacanthus var. baltica
Author: Grunow 1880
Diameter: 30-80 µm
Rows of areolae in 10 µm:

Original Description

Original Images

Cite This Page:
Burge, D., and Edlund, M. (2015). Thalassiosira baltica. In Diatoms of the United States. Retrieved April 22, 2018, from

Species: Thalassiosira baltica

Contributor: David R.L. Burge | Mark Edlund

Reviewer: Pat Kociolek


Cleve, P.T. and Grunow, A. (1880). Beiträge zur Kenntniss der Arktischen Diatomeen. Kongliga Svenska-Vetenskaps Akademiens Handlingar, 17(2): 121 pp., 7 pls.

Edlund, M.B., Taylor, C.M., Schelske, C.L. and Stoermer, E.F. (2000). Thalassiosira baltica (Bacillariophyta), a new exotic species in the Great Lakes. Canadian Journal of Fisheries and Aquatic Sciences 57: 610-615.

Hasle, G.R. (1978). Some freshwater and brackish water species of the diatom genus Thalassiosira Cleve. Phycologia 17: 263-292. 10.2216/i0031-8884-17-3-263.1

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Thalassiosira baltica CAS

NCBI Genbank Taxonomy

Thalassiosira baltica NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 70001

Autecology Discussion

Thalassiosira baltica is regarded as a non-native species in North America because it was recently introduced to the Laurentian Great Lakes (Edlund et al. 2000). This taxon was originally described from the Baltic Sea and is similar to many other euryhaline species. The observed range in diameter for North American freshwater populations of T. baltica is much smaller than the observations by Hasle (1978) in the Baltic Sea (20-120 µm).

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

Thalassiosira baltica

EMAP Response Plots

Thalassiosira baltica

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.