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| Abstract Submission No. | ABS-2022-05-0302 |
| Title of Abstract | What controls the initiation of algal bloom during the winter monsoon in the Arabian Sea?? |
| Authors | Lakshmi Shenoy*, Satya Prakash, Aneesh Lotliker, Sanjib Baliarsingh, Teesha Mathew, Abhisek Chatterjee, Biraj K Sahu, T M Balakrishnan Nair |
| Organisation | INCOIS |
| Address | Vatheriparambil House, Behind Balakrishna Swamy temple, Kuzhuppilly, Ayyampilly Ernakulam, Kerala, India Pincode: 682501 Mobile: 8547840359 E-mail: shenoy.laks107@gmail.com |
| Country | India |
| Presentation | Poster |
| Abstract | Occurrence of phytoplankton bloom in the northern Arabian Sea (NAS) during winter monsoon is perplexing. The convective mixing leads to a deeper and well oxygenated (>95% saturation) mixed layer. We encountered low chlorophyll condition though the nutrient conditions were favorable for a bloom. The mean ratio of silicate to NOx (nitrate + nitrite + ammonium) in the upper 100 m was 0.72 indicating ⿿Silicate stressed condition for the proliferation of diatoms. Also, the euphotic depth (~49 m) was much shallower than the mixed layer (~110 m) suggesting the Sverdrup critical depth limitation in the NAS. We show that the bloom in this region initiates only when the mixed layer shoals towards euphotic zone. Our observations further suggest that two primary factors, stoichiometric ratio of nutrients, especially Si/N ratio, in the mixed layer and re-stratification of the upper water column, govern the phytoplankton blooming in NAS during the later winter monsoon. |