• Category
  • Length Range
    45.6-78.3 µm
  • Width Range
    11.4-15.3 µm
  • Striae in 10 µm
  • Synonyms
    Cymbella helvetica var. compacta (Østrup) Hust. 1955
  • Reported As
    Cymbella helvetica (Krammer and Lange-Bertalot 1986, figs 133: 4, 5)



Valves are dorsiventral with an arched dorsal margin and a slightly convex to nearly flat ventral margin. The apices are rounded and may become weakly protracted in larger specimens. The axial area is narrow and positioned just ventral of the valve mid line. The central area is small and elliptic in shape, or absent. Four to eight elongated areolae present at the proximal ends of median ventral striae. The raphe is lateral, becoming filiform near the proximal and terminal ends. Proximal raphe ends are hooked toward the ventral margin. Terminal raphe fissures are deflected dorsally at a 45 degree angle. Striae are radiate, becoming parallel, and then convergent near the apices. The striae continue around the valve apices. Areolae are distinct in LM and number 22-25 in 10 µm.


Krammer (2002) reports Cymbella compacta to be widespread in eutrophic habitats with pH above 7. The specimens shown on this web page are from two streams in the Black Hills of western South Dakota. Geologically and ecologically, the Black Hills are considered an "island range" of the middle Rocky Mountains.

Little Spearfish Creek Sd
Credit: Loren Bahls
Little Spearfish Creek, Black Hills, South Dakota: home of Cymbella compacta

Original Description

  • Author
    Østrup 1910
  • Length Range
    29 µm
  • Width
    12 µm
  • Striae in 10µm

Original Images

Cymbella compacta orig illus
Cymbella compacta orig descr

Cite This Page

Bahls, L. (2016). Cymbella compacta. In Diatoms of North America. Retrieved April 16, 2024, from https://diatoms.org/species/cymbella_compacta


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Cymbella compacta 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.