• Category
  • Diameter
    13-32 µm
  • Synonyms
    Cyclotella punctata W.Sm. 1856
    Stephanodiscus punctatus (W.Sm.) Grunow 1878
  • Reported As
    Thalassiosira bramaputra ((Ehrenb.) Håk. and Locker 1981)



Valves are rounded and tangentially undulate on the valve face. Areolae are rectangular to irregular in shape and organized into radial rows of coarse striae that may appear slightly disorganized. A ring of marginal fultoportulae is present. These fultoportulae have external tubes, giving the impression of a ring of short spines around the valve periphery. A prominent rimoportula is present on the valve face, close to the margin.

This taxon has been misidentified as T. bramaputra, which has not been verified in North America. According to Smucker et al. (2008), Thalassiosira bramaputrae has two marginal rings of evenly spaced fultoportulae. In contrast, T. lacustris has one complete ring of marginal fultoportulae and an inner ring of irregularly spaced occluded processes. The inner ring of proccesses number about half the number of marginal fultoportulae.


Original Description

  • Basionym
    Coscinodiscus lacustris
  • Author
    Grunow in Cleve and Grunow 1880

Cite This Page

Kociolek, P. (2011). Thalassiosira lacustris. In Diatoms of North America. Retrieved May 16, 2021, from https://diatoms.org/species/thalassiosira_lacustris


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