• Category
  • Length Range
    59-79 µm
  • Width Range
    8.0-8.7 µm
  • Striae in 10 µm
  • Reported As
    Pinnularia subgibba var. gracilis (E.E.Gaiser and J.Johansen 2000)



Valves are linear, with slightly undulate margins and rostrate apices. The axial area is wide, sometimes appearing granular. The axial area gradually widens toward the central valve, forming a narrowly elliptic, sometimes swollen, central area. The raphe is broad, with comma-shaped terminal fissures. Striae are parallel in the valve center becoming convergent near the apices. A transverse fascia is not present in this taxon.

We consider the taxon, Pinnularia subgibba var. gracilis, to be a later homonym of P. feremorosa.


This taxon was verified in lakes in the northeastern US, as well as in lakes of South Carolina and Florida.

Original Description

  • Author
    Metzeltin and Lange-Bert. 2007
  • Length Range
    65-112 µm
  • Width
    8-10.5 µm
  • Striae in 10µm

Original Images

Pinn feremorosa org img
Pinn feremorosa org desc

Cite This Page

Aycock, L. (2022). Pinnularia feremorosa. In Diatoms of North America. Retrieved May 30, 2024, from https://diatoms.org/species/pinnularia-feremorosa


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