• Category
  • Length Range
    5-19 µm
  • Width Range
    3-5 µm
  • Striae in 10 µm



Valves are broadly linear to nearly elliptical in outline with rounded ends. The axial area narrow at the poles, widening to form a linear-elliptical to lanceolate central area. The raphe is straight, filiform, with distal ends not reaching the apices. The proximal raphe ends terminating quite a distance from one another. Striae are prominent, without visible punctuation in the LM, and radiate throughout.

Comments: Valve ultrastructure was used (Krammer 2000) to differentiate this genus from Pinnularia; this is the only species of the genus known in the US flora. This taxon is found in cool or mountainous regions across the US.


Original Description

  • Basionym
    Pinnularia balfouriana
  • Author
    Grunow ex Cleve 1895

Original Images

Pinnularia Balfouriana Orig Desc Plate
Pinnularia Balfouriana Orig Desc Text

Cite This Page

Kociolek, P. (2011). Hygropetra balfouriana. In Diatoms of North America. Retrieved June 23, 2024, from https://diatoms.org/species/hygropetra_balfouriana


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