• Category
  • Length Range
    9.7-18.6 µm
  • Width Range
    2.5-3.8 µm
  • Striae in 10 µm



Valves are slightly dorsiventral and lanceolate with weakly convex dorsal and ventral margins. Apices are broadly rounded, about half the valve width, subrostrate to subcapitate. The axial area is narrow, merging with a small, slightly wider central area. Raphe branches are filiform and bowed, concave to the dorsal margin. Proximal raphe ends are unexpanded and deflected dorsally. Striae are parallel to weakly radiate. The central 2-3 striae on each side are more distant from their neighbors than are the remaining striae.


Encyonopsis perborealis is widely distributed and locally abundant in higher elevation lakes and streams in the northern Rocky Mountains. At sites with water quality data, pH varies from 8.0 to 9.0 and specific conductance from 100 to 176 µS/cm (Bahls 2013). The type locality of E. perborealis is a lake in northern Norway. Krammer (1997) also reports this species from lakes in Lapland.

North Fork Flathead
Credit: channeloutfitters.com
North Fork of the Flathead River near the Montana- British Columbia boundary: home of Encyonopsis perborealis.

Original Description

  • Author
    Krammer 1997
  • Length Range
    11-20 µm
  • Width
    2.5-3.5 µm
  • Striae in 10µm

Original Images

Encyonopsis Perborealis Origimag025
Encyonopsis Perborealis Origdesc024

Cite This Page

Bahls, L. (2013). Encyonopsis perborealis. In Diatoms of North America. Retrieved April 16, 2024, from https://diatoms.org/species/encyonopsis_perborealis


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