Characterization of phytoplankton productivity and bio-optical variability in a polar marine ecosystem
| Autor: | Amit Sarkar, S. C. Tripathy, David J. Hughes, P. Sabu, Manish Tiwari, Sudarsana Rao Pandi, Anvita U. Kerkar |
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| Rok vydání: | 2021 |
| Předmět: |
0106 biological sciences
Water mass 010504 meteorology & atmospheric sciences Range (biology) 010604 marine biology & hydrobiology Geology Aquatic Science Oceanography 0403 Geology 0405 Oceanography 01 natural sciences Carbon cycle Nutrient Productivity (ecology) Phytoplankton Environmental science Marine ecosystem Absorption (electromagnetic radiation) 0105 earth and related environmental sciences |
| Zdroj: | Progress in Oceanography. 195:102573 |
| ISSN: | 0079-6611 |
| Popis: | Knowledge of Southern Ocean carbon cycling is limited by a paucity of phytoplankton primary productivity (PP) and spectral absorption data in this globally-important region. We measured 13C-based PP in the Indian sector of Southern Ocean (ISSO) during austral summer 2017, examining its link with spectral absorption coefficients and phytoplankton size structure derived from an absorption-based global model. Phytoplankton productivity was assessed at both coastal (60°S-69°S) and frontal stations (40°S-60°S), characterized by silicate- replete and -deplete water masses, respectively (indicated by measured nutrient ratios) to capture a range of phytoplankton growth conditions. Bio-optical relationships were used as indicators of phytoplankton community size structure and to assess the extent of cellular pigment packaging - a phenomenon reported previously for phytoplankton in this region. Blue-Red (B/R) ratios of phytoplankton absorption (aph) spectra indicated that microphytoplankton (more prone to “package effects”) were the dominant size class at most sites sampled. Overall, PP was better explained by aph (R2 = 0.85) than total chlorophyll-a (R2 = 0.64) in surface waters. The a*ph (675)-chlorophyll-a relationship explained package effects more effectively in frontal regions (R2 = 0.63) than stations further south (R2 = 0.30). The global absorption-based model captured smaller (pico, nano) phytoplankton size classes but failed to identify larger microphytoplankton, underscoring the need for region-specific algorithm modifications. Our findings improve existing understanding of spatio-temporal trends in PP and bio-optical variability within the Indian Sector of the Southern Ocean (ISSO) – knowledge that is essential to improve capacity to retrieve PP from satellite-based models in this region. |
| Databáze: | OpenAIRE |
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