Seasonal and spatial variations of mesozooplankton energy transfer efficiency determined using remotely sensed SST and Chl-a in the Bay of Bengal

Mesozooplankton (MSP) are the major group of secondary producers in the ocean. They play an important role in both the carbon flux and energy transfer from primary producers to higher trophic levels. The present work explores the significance of how MSP biomass relates to the energy transfer between primary and secondary trophic levels by applying the MSP biomass model developed and validated by Mahesh et al. (2018) in the Bay of Bengal (BoB). The remote sensing products, mean sea surface temperatures (SST) and chlorophyll-a (Chl-a), were acquired from the Aqua (EOS PM) satellite’s Moderate Resolution Imaging Spectroradiometer (MODIS) sensor for the pre-monsoon period in 2013 through to summer 2015. These data were incorporated into the model to estimate MSP biomass which ranged from 0.12 to 33.52 mg C m−3 in the summer and post-monsoon periods in 2014, respectively, and was statistically significant between the seasons (F=19. 43; P=0. 008). The MSP productivity rate varied from 0.07 (summer 2014) to 15.35 mg C m−3 d−1(post-monsoon 2015). The rate was low (1 mg C m−3 d−1) across the central bay during the pre-monsoon period, whilst it was slightly higher (1-3 mg C m−3 d−1) along the neritic waters of the Palk Bay and Kakinada coastlines. The mean energy transfer efficiency from primary producers to MSP production was between 8.81 and 62.36 % during the post-monsoon and summer periods, respectively. This varied significantly between seasons (F=16.61; P=0.005) and was higher in the central bay than coastal waters. The complex interactions between water temperature, primary producer abundance, MSP grazing potential, seasonal variability, and the influential role of monsoons were the major controlling factors governing MSP biomass across the BoB. [Display omitted] •Mesozooplankton’s energy transfer efficiency was estimated from 2013 to 2015 in the Bay of Bengal.•Present study provides a novel approach to estimate energy transfer efficiency of mesozooplankton.•Present study indicates pre-monsoon period was most productive season for mesozooplankton in the Bay of Bengal.