• Category
  • Length Range
    112.0-221.2 µm
  • Width Range
    25.2-38.5 µm
  • Striae in 10 µm
    7-9 at the valve center, 10-11 near the apices



Valves are dorsiventral, with rounded apices. The dorsal margin is distinctly arched and the ventral margin is slightly concave, with a gibbous middle portion. The central area is only slightly wider than the axial area. The central area is asymmetric, rounded on the dorsal side and nearly flat on the ventral side. The ventral side of the central area is bordered by irregularly spaced areolae. Stigma or stigmata are absent. The raphe is narrow near the proximal ends and is deflected slightly toward the ventral margin. The proximal raphe ends are expanded. Terminal raphe fissures are sickle-shaped and deflected dorsally. Striae are radiate throughout. Areolae are distinct and number 9-11 in 10 µm.


Cymbella aspera is widely distributed in alkaline waters with low nutrients and low to moderate electrical conductance, but seldom found in large numbers. It is often encountered in lakes, ponds, fens, springs and creeks in the northern Rocky Mountains.

Atlantic  Pond
Credit: Loren Bahls
Atlantic Pond, Glacier National Park, Montana: home of Gomphonema duplipunctatum.

Original Description

  • Basionym
    Cocconema asperum
  • Author
    Ehrenb. 1840

Original Images

Cocconema asperum orig illus

Cite This Page

Bahls, L. (2016). Cymbella aspera. In Diatoms of North America. Retrieved April 21, 2024, from https://diatoms.org/species/cymbella_aspera


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Cymbella aspera from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.