• Category
  • Length Range
    16.6-21.9 µm
  • Width Range
    7.0-8.3 µm
  • Striae in 10 µm
  • Synonyms
    Achnanthes depressa (Cleve) Hust.
  • Reported As
    Achnanthes depressa (Krammer and Lange-Bertalot 1991, pg. 17, Pl. 9, Fig 11-13)



Valves are broadly elliptic-lanceolate, with rostrate to subcapitate ends. Frustules are strongly arched, a feature most evident in girdle view. The raphe valve is concave and the rapheless valve is convex. The raphe valve has a narrow axial area and a transapically expanded central area. The raphe is slightly bent, with expanded proximal raphe ends. The rapheless valve has a narrow, linear axial area and a somewhat larger central area, which is variable in shape.


Eucocconeis depressa has been found in several wetland ponds, shallow lakes and streams in the Alaskan arctic. The pH of these waters was low, at 5.1-6.6. Specific conductance was also low, at 39-185 µS/cm. This taxon was also reported from Adak Island, Alaska in both lakes and streams (Hein 1990).

Original Description

  • Basionym
    Navicula depressa
  • Author
    Cleve 1891
  • Length Range
    22 µm
  • Width
    9 µm
  • Striae in 10µm

Original Images

Nav Depressa Orig Ill001
Navicula Depressa Origdesc

Cite This Page

Bogan, D. (2016). Eucocconeis depressa. In Diatoms of North America. Retrieved June 21, 2024, from https://diatoms.org/species/eucocconeis_depressa


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