01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-06-0283 |
| Title of Abstract | Seasonality and spatial distribution of secondary chlorophyll maxima in the Arabian Sea based on BGC-Argo Data |
| Authors | Siby Kurian*, Ameen Muhammed P.P, Damodar M. Shenoy, J. Pavan Kumar, TVS. Udaya Bhaskar, Nikhil Bhujbal, Smita Mitbavkar, Anil K.Pratihary |
| Organisation | CSIR-National Institute of Oceanography |
| Address | CSIR- National Institute of Oceanography North Goa, Goa, India Pincode: 403004 E-mail: siby.nio@csir.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | The Arabian Sea (AS) is a vital component of the Indian Ocean, playing a crucial role in regional climate patterns and ocean dynamics. The AS is one of the highly productive regions in the world's oceans, characterized by an intense OMZ in its subsurface depths. Apart from the primary chlorophyll maxima, a secondary chlorophyll maximum (SCM), mainly contributed by picoplankton, Prochlorococcus, was also reported in the AS. Mostly, the SCM was reported in the southern boundary of the AS OMZ, mainly during the northeast monsoon (NEM) season. Here, we use biogeochemical data from the Argo floats deployed from 2013 to 2025 to find the seasonal variability and spatial distribution of SCM in the AS, and also to understand the factors responsible for its occurrence. By investigating 438 profiles having a SCM, our study indicates that it mostly occurs during the NEM and spring inter-monsoon (SIM), but also appears during the Southwest monsoon (SWM). Spatially, these peaks were found not only at the southern boundary of the AS OMZ, but it was also present throughout the OMZ. Based on two case studies on BGC floats in the AS, it was found that the SCM forms just above the upper boundary of the OMZ. It's also noticed that the occurrence or disappearance of SCM in the AS is mostly linked to the shoaling or deepening of the upper boundary of OMZ. The SCM is well developed when the upper boundary of the OMZ is shallow, and under optimum light and secondary nitrite availability, Prochlorococcus probably proliferates. This was also validated with insitu water column data on picoplankton and marker pigments. Overall, our results confirm the presence of SCM as a consistent and dynamic feature of the AS and warrant further studies on its role in carbon transfer and feedback to the OMZ. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Secondary Chlorophyll Maxima, Arabian Sea, BGC-Argo Data, Marker Pigments, OMZ |
| For Awards | no |