Lunar rhythm in the planktonic biomass of Bay of Bengal at Digha-on-sea (W. B.)

The lunar cycle imparts certain stimulating effects on the rhythmic behaviour of plankton and their life processes by which they actively migrate to the sea surface and gradually sink as the moon fades, This may result in morphological changes in Organisms, such as Lorica which becomes smaller towards the full moon night by changing the size of postero lateral spines and surface area. In addition Cyclo-morphic forms have been observed in zooplankton, that seems to be a suitable achievement for reproductive purposes such as swarming and for the differentiation of sex by secondary sexual character. Lunar rhytham in plankton appears to be governed by an internal clock, otherwise called as the “Biological Clock”. The plankton (Phyto-zoo plankton) exhibiting their numerical rhythms in response to lunar cycle have become evident from this study (i.e. 2013). On the full moon light the total planktonic Biomass was highest in comparison to the other phases of lunar cycle. The physico-chemical parameters which showed certain positive effect on the lunar cycle caused congenial condition. In relation to lunar advancement certain morphological changes (Cyclomorphosis) of forms were reported in some Rotifera, Cladocera and Copepoda.