Monsoonal Pattern Impact on Phytoplankton Size Classes Distribution in the Arabian Sea

Of the many oceanic ecosystems experiencing anthropogenic and climate-driven changes worldwide, the Arabian Sea (AS) stands out as the one with the most dramatic and extreme changes of all. Notably, the distinct driven factor is the monsoon which plays an important role in phytoplankton dynamics and biogeochemical cycles in the AS. Besides phytoplankton communities are extremely sensitive to environmental condition that specifically dictates by nutrient and light availability, with related consequences for the marine food web and for primary production. To address the monsoonal pattern influence on phytoplankton community dynamics, we have retrieved the distribution of phytoplankton communities based on their size (micro- >20 μm, nano- 2 - 20 μm and pico phytoplankton- < 2 μm) using abundance based approach. Further we have investigated how the specific phytoplankton size classes (PSCs) respond to monsoonal patterns in the AS. Our results indicate that the micro are found to be dominated in Northern AS and Western AS particularly during summer and winter monsoon period respectively due to nutrient uptake from upwelling process. Whereas pico found to be dominated during the inter-monsoon period in the southern part of the AS because of oligotrophic condition. Though the nano has the unique capability of ubiquitous behaviour which could survive under any condition. Yet, the dominance of micro and pico in the particular region during monsoon induces the nano to shift which is ideal behaviour encountered in the AS. Overall the study highlights the influence of monsoonal pattern for the PSCs distribution and the unique adaptation of PSCs which was not reported in any of the previous studies, especially in the AS.