Visit us at

Diatoms of the United States is now known as Diatoms of North America.
This site has been redesigned and updated, and will be closing soon.

Cocconeis fluviatilis

J.H.Wallace 1960      Category: Monoraphid

Chamaepinnularia soehrensis


Cocconeis klamathensis

LM scalebar = 10 µm = 40 pixels.


Contributor: Marina Potapova - November 2010
Length Range: 20-24 µm
Width Range: 13-19 µm
Striae in 10 µm: 12-13


Valves are elliptic. The raphe valve has a narrow axial area and a vary small circular central area, or no distinct central area at all. The raphe is straight and filiform. The distal raphe ends are straight and expanded externally. The proximal raphe ends are externally straight and slightly expanded. Striae are radiate and interrupted by a hyaline rings positioned close to the valve margin. Areolae are usually well distinguished under LM, and number15-25 in 10 µm. Areolae are arranged into longitudinal rows. The rapheless valve has a linear to linear-lanceolate axial area and radiate striae. Areolae are much smaller in the raphe valve than in rapheless valve, but in both valves areolae are smaller near the axial area. Areolae become conspicuously larger toward the valve margin.

Original Description

Author: J.H.Wallace 1960
Length Range: 23-24 µm
Width Range: 13-19 µm
Striae in 10 µm: 16 along raphe, 12 near margin

Original Description

The rapheless valve is somewhat similar to Cocconeis intermedia Herib. and Perag. It differs from this in that the puncta which make up the striae in this new species become progressively heavier and longer as they approach the valve margin, 16 striae in 10 μ in the middle (as measured along the raphe) and 12 striae in 10 μ at the margin. The raphe valve has the same striae count, but the striae are finely punctate throughout. An interruption, as found in Cocconeis placentula Ehr. and its varieties is present, but the lower striae number in this species removes it from the Cocconeis placentula complex.

Original Images

Original text and images reproduced with permission by Academy of Natural Sciences of Philadelphia.

Cite This Page:
Potapova, M. (2010). Cocconeis fluviatilis. In Diatoms of the United States. Retrieved May 25, 2018, from

Species: Cocconeis fluviatilis

Contributor: Marina Potapova

Reviewer: Kalina Manoylov


Wallace, J. (1960). New and variable diatoms. Notulae Naturae 331: 1-8.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Cocconeis fluviatilis CAS

North American Diatom Ecological Database (NADED)

NADED ID: 16010

Autecology Discussion

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

Cocconeis fluviatilis

EMAP Response Plots

Cocconeis fluviatilis

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.