• Category
  • Length Range
    19.6-48.7 µm
  • Width Range
    6.0-10.8 µm
  • Striae in 10 µm
    12-14 at the valve center, 15-17 near the apices
  • Synonyms
    Cymbella silesiaca Bleisch in Rabenh. 1864
  • Reported As
    Cymbella minuta var. silesiaca (Patrick and Reimer 1975, pg. 49, Pl 8, Figs 7-10)
    Cymbella silesiaca (Krammer and Lange-Bert. 1986, pg. 304, Pl 117, Figs 1-24)



Valves are dorsiventral, with rounded apices. The dorsal valve margin is strongly convex. The ventral valve margin is slightly convex, often with a tumid center. The maximum length to width ratio is 4.3. The axial area is narrow and confluent with a slightly wider central area. Proximal raphe ends are slightly inflated and deflected dorsally. Distal raphe ends are curved toward the ventral margin. Dorsal striae are radiate. A single stigmoid lies at the proximal end of the middle dorsal stria. Ventral striae are radiate near the valve center, becoming convergent toward the apices. Areolae number 28–32 in 10 μm.


This is one of the most common species in flowing waters of the northern Rocky Mountains, where it is found under a wide range of water quality conditions (see table below). It sometimes dominates diatom associations in waters contaminated with heavy metals from abandoned hard rock mines.

Encyonema Silesiacum Autecology
Credit: Montana Diatom Database
Weighted average values for selected water quality variables measured during collections of Encyonema silesiacum in Montana.

Original Description

  • Basionym
    Cymbella silesiaca
  • Author
    Bleisch in Rabenh. 1864

Cite This Page

Bahls, L. (2016). Encyonema silesiacum. In Diatoms of North America. Retrieved July 15, 2024, from https://diatoms.org/species/encyonema_silesiacum


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