Diatoms of North AmericaDiatoms of North America

Eunotia bactriana

Ehrenb. 1854

Eunotia Bactriana Guide
  • Category
    Eunotioid
  • Length Range
    31.4-38.4 µm
  • Width Range
    5.0-6.4 µm
  • Striae in 10 µm
    14-16 at mid-valve; up to 18 at valve ends

Identification

Eunotia bactriana LM1 Eunotia bactriana LM2 Eunotia bactriana LM3 Eunotia bactriana LM4 Eunotia bactriana LM5 Eunotia bactriana LM6 Eunotia bactriana LM7
View image metadata
Eunotia bactriana SEM1

Description

Valve outline is complex. The dorsal margin is convex and contains two prominent, pointed, widely-set undulations. Between these undulations, the dorsal margin may become less uniformly convex in smaller valves. The ventral margin is concave but becomes more linear in smaller specimens. The ventral margin also has subtle undulations where the valve is widest. Apices are capitate and dorsally recurved. Terminal raphe ends are visible near the apices. Striae are evenly spaced through most of the valve, becoming slightly denser at the apices. Areolae are dense and only barely visible with ideal illumination in LM.

Autecology

This taxon is rare, occurring across a wide geographical range but absent from large parts of Europe and North America, primarily limited to alpine, boreal, subarctic and arctic habitats (Lange-Bertalot et al. 2011). It has been reported with light micrographs from lakes in the Northeastern US (Camburn and Charles 2000), and Oregon (Bahls 2021).

In the Great Lakes National Parks (Edlund et al. 2009, 2011, 2012, 2013), this taxon is rare (0.1-1% abundance) at Apostle Islands (Outer Lake). It is reported to occur in mountain lakes with cool circumneutral to moderately acidic water of very low conductivity (Lange-Bertalot et al. 2011, Bahls 2021). Reported to occur in oligotrophic to dystrophic systems (Lange-Bertalot et al. 2011). The population imaged above was collected at Kings Lake Bog, a small, well protected, oligotrophic, lowland sphagnum bog in the Puget Trough (Lebednik and del Moral 1976).

Several research groups consider this taxon an indicator organism and published regional environmental optima and tolerances including:

Camburn and Charles (2000): pH - 5.13 +/- 0.45, Acid Neutralizing Capacity - (-2) +/- 12 µeq/L, Total Aluminum - 257 +/- 185 µg/L, Dissolved Organic Carbon - 149 +/- 100 µmol/L, Total Phosphorus - 3.58 +/- 2.77 µg/L for populations from the Northeastern US.

Original Description

  • Author
    Ehrenb. 1854

Original Images

Eunotia bactriana orig illus

Citations & Links

Citations

Links

  • Index Nominum Algarum
    Original
  • North American Diatom Ecological Database
    NADED ID: 33003

Updates

Feb 05, 2026 - Addition of Autecology and SEM

From 2016 until 2026, the autecological information on this taxon page was limited. As of this update, a SEM and information on ecology, biogeography, and environmental optima have been added. - Lane Allen and Mark Edlund

Cite This Page

Bishop, I., Edlund, M., Allen, L. (2016). Eunotia bactriana. In Diatoms of North America. Retrieved March 23, 2026, from https://diatoms.org/species/51342/eunotia_bactriana

Responses

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