• Category
  • Diameter
    6-10 µm
  • Striae in 10 µm
    8-13 based on circumferential density
  • Synonyms
    Stephanodiscus astraea var. minutula (Kütz.) Grunow in Van Heurck
    Stephanodiscus minutulus (Kütz.) Cleve and J.D.Möller
    Stephanodiscus minutulus Grunow



Valves are small and disc-shaped, with a concentrically undulate valve face. Valve faces are complementary, with scutate (raised) and lacunate (depressed) valves. Areolae are scattered at the valve center and arranged in multiseriate fascicles toward the margin. Areolae number 2-3 per fascicle near the margin, but in many specimens, the areolae may not be resolvable at the margin. The interfascicles are narrow and uniform in width. They may vary across specimens by being either wavy or straight. A small spine is present between each fascicle, at the interfascicle and face/mantle junction. A single fultoportula is present near center of the valve face, a feature is usually not observable in LM. Marginal strutted processes are located on the mantle beneath every 4-5th spine.


The planktonic species S. minutulus is common in meso- to eutrophic lakes and large rivers of North America (Cumming et al. 1995, Reavie and Smol 1998, Reavie and Kireta 2015). In the Laurentian Great Lakes, it reaches its greatest abundance in productive nearshore regions, the mouths of large rivers and coastal embayments (Stoermer and Yang 1969). Increased abundance of S. minutulus in paleolimnological records is a strong indicator of cultural eutrophication (Reavie et al. 2000).

Stephanodiscus Minutulus
Credit: USGS/Biodata
Distribution of Stephanodiscus minutulus in streams of the continental United States.

Original Description

C. minor, latere secundarie radiatim striato, flexuoso.

  • Basionym
    Cyclotella minutula
  • Author
    Kütz. 1844
  • Length Range
    10 µm

Original Images

Cyclotella minutula orig descr

Citations & Links



Cite This Page

Burge, D, and Edlund, M. (2017). Stephanodiscus minutulus. In Diatoms of North America. Retrieved July 23, 2018, from https://diatoms.org/species/stephanodiscus_minutulus


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