Satellite observations of Indian Ocean Dipole driven winter chlorophyll enhancement and phytoplankton size structure in the southeastern Bay of Bengal.
Date
2026Author
John, J.
Adith, V.B.
Akhil, V.P.
Keerthi, M.G.
Joy A.J.
Kurian, S.
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Winter surface chlorophyll (SChl) in the southeastern Bay of Bengal (SEBB) exhibits pronounced interannual variability associated with positive Indian Ocean Dipole (IOD) events. Elevated SChl concentrations occur during strong positive IOD years and are primarily driven by remotely forced ocean dynamics, particularly Rossby wave-induced changes in upper ocean stratification and nutrient redistribution. Satellite observations during these winters reveal coherent increases in SChl and total phytoplankton carbon biomass, accompanied by a distinct coastal-to-offshore gradient in phytoplankton community size structure. Microphytoplankton biomass is largely confined to nutrient enriched coastal waters near the eastern boundary, whereas nanophytoplankton dominate biomass enhancement across coastal and intermediate waters. Offshore regions are increasingly dominated by picophytoplankton under low nutrient environments. Picophytoplankton carbon biomass persists even when SChl anomalies weaken, indicating a partial decoupling between SChl concentration and phytoplankton biomass. These findings highlight the importance of resolving phytoplankton size classes and carbon biomass alongside SChl, as different size groups respond distinctly to climate driven physical forcing and nutrient availability in nutrient limited tropical oceans.
URI
https://www.tandfonline.com/doi/full/10.1080/2150704X.2026.2662544http://drs.nio.res.in/drs/handle/2264/9663
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- Scholarly literature [9297]

