• Category
  • Length Range
    50-75 µm
  • Width Range
    2.0-2.5 µm
  • Striae in 10 µm



Valves are narrow and lanceolate, with attenuated, capitate apices. The mid-valve has convex margins. In girdle view, frustules are somewhat rectangular and wider at mid-valve. The axial area is lanceolate and in some specimens a distinct fascia is present in the central area. Striae are distinct, but areolae are resolvable under LM. Striae are parallel throughout the valve and extend midway onto the valve mantle. Costae are wider than the striae.


Cells may form small colonies, joined by linking spines. This taxon is a common member of the plankton.

Original Description

  • Basionym
    Synedra tenera
  • Author
    W.Sm. 1856

Original Images

Fragilaria Tenera Description

Cite This Page

Morales, E., Rosen, B. (2013). Fragilaria tenera. In Diatoms of North America. Retrieved June 13, 2024, from https://diatoms.org/species/fragiaria_tenera


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