• Category
  • Length Range
    34-90 µm
  • Width Range
    11-15 µm
  • Striae in 10 µm
    11-12 at the center, 14-16 at the poles



Valves lanceolate-clavate, with headpole rounded and slightly protracted. Footpole rounded. Valve tapers gently towards the headpole, more strongly towards the footpole, especially in shorter specimens. The raphe is undulate and lateral. The axial area is narrow at the poles, straight, widens at the center to form a small, somewhat rounded central area. A single round stigma is found in the central area. Striae are radiate throughout the length of the valve. Longitudinal lines are positioned on either side of the axial area; they are indistinct in some specimens. The apical pore field is small. This species is known only from Montana.

Comments: These metrics for length and breadth indicates valves can be slightly smaller (down to 34 µm in length, and 11 µm in breadth) than indicated in Kociolek et al. (1986)


Original Description

  • Basionym
    Gomphonema septum
  • Author
    Moghadam 1969

Cite This Page

Kociolek, P. (2011). Gomphoneis septa. In Diatoms of North America. Retrieved July 15, 2024, from https://diatoms.org/species/gomphoneis_septa


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