• Category
  • Length Range
    16-35 µm
  • Width Range
    4.1-7.0 µm
  • Striae in 10 µm
    14-18 in the center valve



Valves are lanceolate with protracted apices. The axial area is narrow and straight. The central area is asymmetric and elliptical. The raphe is straight, with external proximal raphe ends sharply bent toward primary side of the valve. Striae are slightly radiate around the center, becoming parallel, then convergent at the apices. The areolae are clearly visible under LM, numbering 25-32 in 10 μm.

Note that the concept presented here is broad. Others (Lange-Bertalot 2001) report that two distinct morphologies are present on the original Donkin microslide. There is additional discussion on N. gregaria and N. supergregaria in Lange-Bertalot (2001, pg. 85-86, figs. 8-25).


This taxon is widespread in lakes and rivers of the US, particularly in sites of high pH, alkalinity, and conductance. It occurs in streams with high embeddedness, turbidity and measures of total human disturbance.

Original Description

Navicula gregaria, n. sp.-Form on S. V. broadly lanceolate, apiculate; striæ obscure.

  • Basionym
    Navicula gregaria
  • Author
    Donkin 1861

Original Images

Navicula Gregaria  Ill
Navicula Gregaria  Descr

Cite This Page

Potapova, M. (2011). Navicula gregaria. In Diatoms of North America. Retrieved July 13, 2024, from https://diatoms.org/species/navicula_gregaria


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