• Category
  • Length Range
    10-23 µm
  • Width Range
    6.0-9.6 µm
  • Striae in 10 µm
    10-12 at the valve center

Identification

Description

Valves are elliptic with cuneate apices. The raphe is straight and filiform with slightly expanded proximal ends. The axial area is narrow and linear. The central area is small and elliptic, and a small stigma appears to be present. Striae are uniseriate and radiate. Striae at the center of the valve are more widely spaced than striae near the apices. The round to apically elongate areolae are coarse, visible under LM, and number 28-36 in 10 µm. Two to four pairs of annulae are present at the apices.

With two to four pairs of annulae at each apex, this taxon clearly belongs in the genus Geissleria and should be considered for nomenclatural transfer. This taxon differs from other species of Geissleria in North America by the coarse areolae. SEM examination is needed to confirm the presence of a stigma.

Autecology

Navicula cascadensis is endemic to the Cascade Mountains of western Oregon. Here it lives in lakes and streams with low electric conductivity (24-38 µS/cm) and slightly acid pH (6.70-6.93).

Orsnw1010 219
Credit: Kirsten Gallo, U. S. Forest Service
Snow Creek, Deschutes County, Oregon: home of Navicula cascadensis

Original Description

  • Author
    Sovereign 1958
  • Length Range
    11-21 µm
  • Width
    6-9 µm
  • Striae in 10µm
    9-11

Original Images

Navicula Cascadensis Origimag001
Navicula Cascadensis Origdesc001

Cite This Page

Bahls, L. (2016). Navicula cascadensis. In Diatoms of North America. Retrieved June 22, 2018, from https://diatoms.org/species/navicula_cascadensis

Responses

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