A report on salinity-governance of auxospore size in euryhaline diatoms of a well mixed estuary on North-Eastern coastal Bay of Bengal

A three yearlong study was performed on the well mixed waters of the Hooghly Estuary on the North-Eastern coast of Bay of Bengal that revealed the significant effect of salinity towards the induction and governance of auxospores and their sizes in euryhaline centric and raphid pennate diatoms. The diatom species were chosen randomly (also due to their ubiquitous nature in the study area) in order to observe the effect of salinity in an unrestrictive manner [viz. Coscinodiscus radiatus Ehrenberg, Coscinodiscus concinnus W. Smith, Coscinodiscus lineatus Ehrenberg, Coscinodiscus excentricus Ehrenberg, Chaetoceros danicus Cleve, Chaetoceros lorenzianus Grunow, Chaetoceros decipiens Cleve, Chaetoceros minimus (Levander) D. Marino, G. Giuffre, M. Montresor & A. Zingone, Pleurosigma formosum W. Smith and Nitzschia sigmoidea (Nitzsch)]. Correlation (r-values at 5% level of significance) values between salinity and auxospore size revealed that lower salinity was conducive for larger auxospore (-0.7391 to -0.9282) production in case of all the species (total ten) studied upon. Nutrient parameters were also found to impart significant influences on auxospore size but not as prominent as salinity. Large auxospore was found to be the prerequisite to greater biovolume and vice versa, pointing to lower salinity regimes of a well mixed estuary favorable for sexual reproduction in euryhaline diatoms.