01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-06-0342 |
| Title of Abstract | Integrating Phytoplankton Photo-Physiological Metrics into Indian Ocean Monitoring: Insights from Fast Repetition Rate Fluorometry in the Arabian Sea |
| Authors | Jagadish S Patil* |
| Organisation | CSIR National Institute of Oceanography |
| Address | Caranzalem Panaji, Goa, India Pincode: 403002 E-mail: patilj.nio@csir.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | Phytoplankton⿿s physiological responses to changes in environmental conditions serve as critical indicators of marine ecosystem health and resilience across the Indian Ocean (IO). This study employs active fluorometry to assess key physiological parameters⿿variable fluorescence (Fv=Fm-F0), photosynthetic efficiency (Fv/Fm), and functional absorption cross-section⿿providing insights into phytoplankton stress responses and ecosystem condition. These photophysiological metrics are influenced by multiple environmental factors, including temperature, salinity, irradiance, and nutrient availability, alongside anthropogenic stressors, necessitating integrated temporal analysis to elucidate underlying physiological mechanisms. While extensive research has documented phytoplankton biomass, productivity, and taxonomic composition throughout IO, systematic assessments of their physiological status remain critically limited. Recent investigations utilising Fast Repetition Rate Fluorometry have significantly advanced understanding of phytoplankton physiological dynamics in monsoonal estuaries and various regions of the Eastern Arabian Sea (from north to south and from coast to ocean). The findings reveal that phytoplankton in the open ocean and coastal areas exhibit spatial variations in photosynthetic efficiency. Notably, frontal zones demonstrate higher photosynthetic efficiency compared to non-frontal regions, attributed to enhanced nutrient availability and optimal light conditions. In contrast, monsoonal estuaries display marked seasonal patterns in photosynthetic performance, directly correlated with monsoon-driven discharge and related environmental changes. Consistent with global oceanic observations, Arabian Sea phytoplankton communities operate at approximately half of the theoretical maximum photosynthetic efficiency (Fv/Fm⿿0.65), reflecting regional oceanographic adaptations. Environmental variability, along with pressures like coastal eutrophication and pollution, significantly affects phytoplankton physiology and ecosystem functioning. The emergence of mixotrophic species such as Noctiluca scintillans further highlights the need for ongoing monitoring. The study emphasises integrating physiological scaling metrics into routine monitoring frameworks to effectively capture responses to variable monsoon systems, climate variability, and intensifying anthropogenic pressures. This approach provides essential early-warning capabilities for detecting ecosystem stress and supports evidence-based management of marine resources in IO under changing environmental conditions. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Phytoplankton, Photosynthetic Efficiency, Fast Repetition Rate Fluorometry, Arabian Sea, Monsoon Dynamics, Ecosystem Monitoring |
| For Awards | no |