• Category
  • Length Range
    114-154 µm
  • Width Range
    24-28 µm
  • Striae in 10 µm



Valves are lanceolate to somewhat rhombic-lanceolate with obtuse, rounded ends. The axial area is barely wider than the raphe at the ends, then widens to three times the width of the raphe near the central area. The central area is rounded and slightly asymmetrical, somewhat shallower on the secondary side than on the primary side of the valve. The raphe is lateral, becoming filiform near the central area, where the proximal ends are hooked toward the secondary side. Striae are radiate throughout most of the valve, becoming parallel and finally somewhat convergent near the ends. Striae are crossed by longitudinal lines, formed by the margin of an internal axial plate. Voigt discontinuities are clearly evident on the secondary side. The areolae are easily distinguished and number about 20 in 10 µm.


Navicula walkeri is an endemic species of the Pacific Northwest, so far reported only from Oregon and California. The type locality is a bay on Wizard Island, Crater Lake National Park. Sovereign (1958) also reports this species as present in nearby Emerald Pool and Diamond Lake, in Spring Creek, Klamath County, Oregon, and as an upper Pliocene fossil in the Terrebonne diatomite beds in northern Oregon. There are three records for Navicula walkeri in the Montana Diatom Collection, all from streams in Oregon, where it prefers circumneutral water with very low concentrations of dissolved solids.

Orsnw1004 111
Credit: U.S. Forest Service photo
Snow Creek, Deschutes County, Oregon, home of Navicula walkeri

Original Description

Valvae rhomboideo-lanceolatae apicibus obtuse rotundatis, non protractis, 108-194 microns longae, 22-29 microns latae. Rhaphe directa, filiformis, poris centralibus internis in eandem partem flexis, fissuris terminalibus longis in eandem partem curvatis. Area axialis modice lata, lanceolata, irregulariter definita, area centralis lata suborbicularis. Costae transapicales circiter 9 in 10 microns, radiantes, prope apices ad lineam mediam perpendiculares, intervalla cum membrana exteriore lineolata, lineolis circiter 20 in 10 microns, in membrana inferiore cum poro elongata juxta marginem.

  • Author
    Sovereign 1958
  • Length Range
    108-194 µm
  • Width
    22-29 µm
  • Striae in 10µm

Original Images

Nwalk Origimag Cropped
Nwalk Origdesc Cropped

Cite This Page

Bahls, L. (2011). Navicula walkeri. In Diatoms of North America. Retrieved May 18, 2024, from https://diatoms.org/species/navicula_walkeri


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