International Journal of Oceans and Oceanography ISSN 0973-2667 Volume 14, Number 1 (2020), pp. 109-124 © Research India Publications https://dx.doi.org/10.37622/IJOO/14.1.2020.109-124 Computational Methods for Long Term Monitoring of New Production and f-ratio Variability in Bay of Bengal D. Poornima 1* , R. Shanthi 1 , R. Ranith 1 , R.K. Sarangi 2 , A. Saravanakumar 1 and T. Thangaradjou 1† 1 Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Tamilnadu, India. † Present Address: Science and Engineering Research Board (SERB), New Delhi, India. 2 Planetary Sciences and Marine Biology Division, Biological and Planetary Sciences and Applications Group, Space Application Centre (ISRO), Ahmedabad - 380 015, Gujarat, India. Abstract MODIS Aqua derived primary production and sea surface temperature (SST) data are used for calculating the f ratio and new production using previously developed models. Developed models were validated with in-situ new production and f ratio values from cruise dataset collected during September 2014. The regression between derived and bottle measured Pnew value showed R 2 =0.553, SEE=±51.632, MNB=-0.414 and RMSE=±266.398. Similarly f ratio is validated with in-situ derived value showed the clear underestimation with a R 2 =0.537, SEE=±0.016, MNB=-0.560 and RMSE=±0.182. The seasonal and inter-annual variation of primary production, f ratio and new production showed the clear seasonal pattern between the seasons. The high (133.64 mgCm -2 d -1 ) and low (31.69 mgCm -2 d -1 ) new production ranges are observed during premonsoon and summer seasons. The integrated primary production and f ratio of all the seasons provides a significant R 2 =0.585. This is used to estimate the total annual primary production of Bay of Bengal as ~11%. The minimum (0.028 GTCyr -1 ) and maximum (0.037GTCyr -1 ) annual new production observed for the years of 2014 and 2006. In the entire processes of primary production, new production rate was less and it indicates Bay of Bengal largely as the regeneration based basin than the new production. Keywords: New production, f ratio, Bay of Bengal, sea surface temperature (SST), MODIS Aqua, Primary production, validation and seasonal