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An experiment was performed taking into account four species each of Coscinodiscus Ehrenberg and
Chaetoceros Ehrenberg to delineate the potential triggering factors inducing auxospores.
Auxospores are sexual spores of diatoms and are normally formed as response to adverse
environmental conditions to curtail the size reduction of diatoms. The parameters considered to be
most important for this purpose are salinity, turbidity, pH and plant nutrients. Two experimental set
ups were established, each of which contained a gradient of all the parameters resulting out of
simulated dilution of the stock media solution to mimic possible conditions experienced by the
subject species in nature. Unfiltered, turbid and filtered, clear natural seawater were employed as
the basic culture media for the two groups of the sets. The various experimental results as well as
statistical data pointed towards salinity and turbidity rather than the more widely accepted
parameters such as nutrients and pH to serve as potential triggering factor. When only salinity was
considered, the auxospore induction appeared to be conservative and 15-22 psu was the range for
optimal generation. The range broadened when turbid water was used and the species developed
auxospores in 8-30 psu of salinity. The potential turbidity range was found to be 80 – 270 NTU
depending upon the presence of auxospores. This experiment shed important lights in the generation
of auxospores and in well mixed estuaries, it might be induced among species near the confluence in
drier periods and can extend to off shore as well during monsoon based on the results obtained.
Key words: Auxospore; Diatom; Hooghly estuary; Salinity; Turbidity