01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-06-0149 |
| Title of Abstract | Understanding Decadal Trend of Algal Blooms in Northern Arabian Sea: An Ocean Colour Remote Sensing Approach |
| Authors | S. Ayana*, Sanjiba Kumar Baliarsingh, Alakes Samanta, Aneesh A. Lotliker |
| Organisation | Indian National Centre for Ocean Information Services (INCOIS) |
| Address | C12 Quarters, INCOIS, Hyderabad ANDHRA PRADESH, Telangana, India Pincode: 500090 E-mail: ayana.s0015@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | The Northern Arabian Sea (NAS) experiences substantial algal blooms during the tropical winter. Significant convective mixing of the water column makes the conducive condition by transporting nutrient-rich subsurface waters to the euphotic zone, favouring high-biomass algal enrichment. Since the early 2000s, traditional diatom-dominated assemblages have been increasingly replaced by the mixotrophic dinoflagellate Green Noctiluca scintillans (GNS), which maintains predator-prey relationships with diatoms. This study employs ocean colour remote sensing to examine spatial and temporal patterns of diatom and GNS distributions across the NAS from 2002 to 2019. Ocean colour algorithms utilizing MODIS-Aqua (MODISA) retrieved Remote Sensing Reflectance (Rrs) to identify and differentiate GNS from diatom assemblages within a heterogeneous phytoplankton community. Algal bloom variability is evaluated through MODISA-retrieved chlorophyll-a concentrations and Sea Surface Temperature (SST). The inverse chlorophyll-a and SST relationship indicated convection-driven nutrient supply mechanisms supporting phytoplankton evolution and growth. Spatial analysis revealed elevated chlorophyll-a magnitude for both algal classes/species during December, representing pre-bloom conditioning phases facilitating subsequent GNS evolution-development. The maximum GNS spread area occurred during February-March. Temporal evolution patterns demonstrate clear indications of mixotrophic predation on diatoms by GNS. Multi-year analysis confirmed February-March as the primary bloom period, with cooler temperatures favouring open-ocean high-biomass bloom episodes. Results indicate marginal increasing trends in overall bloom intensity, characterized by stable diatom distributions but slight increases in GNS spatial coverage. MODISA retrieved information provided a robust analytical framework for monitoring long-term phytoplankton community dynamics and succession patterns in NAS. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Noctiluca; Diatom; Chlorophyll-a; Arabian Sea; MODISA |
| For Awards | no |