• Category
  • Length Range
    18.6-34.5 µm
  • Width Range
    4.8-6.3 µm
  • Striae in 10 µm



Valves are rhombic-lanceolate and weakly heteropolar. Apices are narrowly rounded and not protracted. The axial area is narrow and linear. The central area is asymmetric and variable and bordered on one side by two shortened striae, each with a single isolated stigmoid near the proximal end. On the opposite side, the central area may be bordered by zero, one or two shortened striae. Raphe branches are lateral and somewhat sinuous. External proximal raphe ends are bent slightly toward the primary side of the valve. Terminal raphe ends are comma-shaped. Striae are radiate near the valve center, often, but not always, becoming parallel near the apices. Central striae are slightly bowed; the remaining striae are straight. Areolae in the striae number 35-40 in 10 µm.

Krasske (1943) described this taxon as Gomphonema bipunctatum, but that name had already been used by Zimmermann in 1915 for a different species with a different type. As such, G. bipunctatum Krasske is an illegitimate name. Lange-Bertalot & Reichardt (1996) gave the type a new name, G. duplipunctatum.


Gomphonema duplipunctatum was described from a moorland pond in Finland that had a pH of 6.5-6.8. In the Northwest U.S. it occurs in small numbers in the Rockies, Cascades and Coast Ranges, where it prefers cold, well-oxygenated and circumneutral waters of low conductivity.

Atlantic  Pond
Credit: Loren Bahls
Atlantic Pond, Glacier National Park, Montana: home of Gomphonema duplipunctatum.
Gomphonema Duplipunctatum Map2
Credit: Montana Diatom Database
Distribution of Gomphonema duplipunctatum in the Northwest United States.
Gomphonema Duplipunctatum Ecology
Credit: Montana Diatom Database
Abundance-weighted mean values for selected water quality variables associated with collections of G. duplipunctatum in the Northwest U.S.

Original Description

Gomphonema Duplipunctatum Origdesc001

  • Basionym
    Gomphonema bipunctatum
  • Author
    Krasske (illegitimate name) 1943
  • Length Range
    18-26 µm
  • Width
    4.5-6.0 µm
  • Striae in 10µm

Original Images

Gomphonema Duplipunctatum Origimag001
Gomphonema Duplipunctatum Origimag002
Gomphonema Duplipunctatum Origdesc001

Cite This Page

Bahls, L. (2017). Gomphonema duplipunctatum. In Diatoms of North America. Retrieved July 13, 2024, from https://diatoms.org/species/gomphonema_duplipunctatum


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