• Category
  • Length Range
    27.1-37.8 µm
  • Width Range
    10.2-13.6 µm
  • Striae in 10 µm
    9-12 at the valve center, more near the apices
  • Reported As
    Eunotia gibbosa (Lange-Bertalot et al. 2011, p. 110, figs. 230: 24-26)
    Eunotia gibbosa (Patrick and Reimer 1966, p. 216, plate 14, fig. 1)
    Eunotia didyma var. inflata (Hustedt in A. Schmidt et al. 1913, figs. 289: 1, 2; Simonsen 1987, p. 39, plate 39, figs. 1-5)



Valves are bilobed and nearly symmetric with respect to the apical axis. The two lobes are separated by a narrow, central isthmus. The dorsal lobes are slightly more closely placed and than the ventral lobes. Valve width at the widest point of the lobes is 10.2-13.6 µm. Valve width at the isthmus is 5.8-8.4 µm. The apices are bluntly rounded and removed from the lobes. Helictoglossae are relatively distant from the apices on the ventral side. Terminal raphe fissures conform to the ventral contours of the valve and are dorsally deflected. Striae are finely punctate and radiate with respect to the isthmus, although some striae of each lobe may also radiate. Short interstriae may be present along both the dorsal and ventral margins. Areolae are difficult to resolve in LM and number 30-35 in 10 µm.


The specimens of Eunotia gibbosa shown here were collected from a lake in the North Cascade Mountains of Washington (photo below) and from Shoofly Meadows in western Montana. Shoofly Meadows is a large, undisturbed complex of marshes, wet meadows, and poor fens in the Rattlesnake Mountains near Missoula. Elsewhere in the United States, E. gibbosa has been recorded from the Adirondack Mountains in New York (Camburn & Charles 2000, Patrick & Reimer 1966), from Bemis Lake, New Hampshire (Lange-Bertalot et al. 2011), and as a fossil from the Kings River, Nevada (Hustedt in Schmidt et al. 1913). This species has not been confirmed outside of North America.

Cutthroat Lake2
Credit: Ryan Davis, Adventurers and Scientists for Conservation.
Cutthroat Lake, Okanogan County, Washington: home of Eunotia gibbosa.

Original Description

  • Author
    Grunow in Van Heurck 1881

Original Images

Eunotia gibbosa orig illus

Cite This Page

Bahls, L. (2014). Eunotia gibbosa. In Diatoms of North America. Retrieved June 19, 2018, from https://diatoms.org/species/eunotia_gibbosa


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