• Category
  • Length Range
    16.7-28 µm
  • Width Range
    8.4-11.2 µm
  • Striae in 10 µm



Valves are lanceolate. The raphe valve has a linear axial area and a rectangular central area, occupying ½ to 2/3 of the valve breadth. The proximal raphe ends are slightly deflected internally. The terminal raphe fissures are long and deflected in opposite directions. The rapheless valve has a narrow axial area and round central area occupying 2/3 of the valve breadth. Striae are radiate. Areolae are 40–60 in 10 μm, with external round foramina, and internal expressions elongated transapically.


So far, Psammothidium lacustre has been found only in oligotrophic lakes of the Washington Cascade mountain range.

Original Description

  • Author
    Enache and Potapova 2013
  • Length Range
    16.7-28 µm
  • Width
    8.4-11.2 µm
  • Striae in 10µm

Original Images

Pslacustre  Orig Ill

Cite This Page

Potapova, M. (2014). Psammothidium lacustre. In Diatoms of North America. Retrieved May 24, 2024, from https://diatoms.org/species/psammothidium_lacustre


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