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| Abstract Submission No. | ABS-2022-06-0151 |
| Title of Abstract | Role of dissolved oxygen in structuring the benthic meiofaunal community off Mumbai, North Eastern Arabian Sea (NEAS) |
| Authors | Sanofar Khokher*, Sabyasachi Sautya, Santosh Gaikwad, Haridevi C.K., Umesh Kumar Pradhan, Udhaba Dora, Heidy Q. Dias |
| Organisation | CSIR-National Institute of Oceanography, Regional Centre, Mumbai |
| Address | CSIR-National Institute of Oceanography, Regional Centre, Mumbai Mumbai, MAHARASHTRA, India Pincode: 400053 Mobile: 7069659909 E-mail: sanofar1641992@gmail.com |
| Country | India |
| Presentation | Poster |
| Abstract | Arabian Sea is known for its profoundly low concentration of dissolved oxygen (DO)(between 150 to 1250 m water depth) due to the biogeochemical process related to monsoonal changes in the region. A low concentration of DO also occurs near to the coast related to the monsoon process as well as anthropogenic eutrophication. The changes in concentration of DO have a direct effect on aquatic organisms especially benthic organisms which are known as secondary producers of the food chain. We aimed to study the benthic meiofaunal community response to DO concentrations during monsoon and its related factors in the surrounding environment from a potential fishery zone off Mumbai. A spatiotemporal variation in meiofaunal assemblages was investigated based on depth gradient (20, 30, 40 & 50m), which was previously known to be a seasonal hypoxic region off Mumbai. The environmental gradients highlighted a significant difference in the bottom environment between depth gradient as well as temporally. The meiofaunal mean density was lower (0.41 ind/10 cm2) at 50 m during November 2017 where DO value has also recorded the minimum (0.3 ml/l). And the highest (5638.06 ind/10cm2) mean density recorded at 20 m depth during April 2017 with maximum DO record (3.23 ml/l). Dissolved oxygen and meiofaunal density showed a positive correlation during the study period. Nematodes (57%) were the numerically dominant meiofaunal taxon at all stations followed by foraminiferans (40%), copepods (1.2%) and polychaetes (<1%). Spearman⿿s rank correlation depicted, variables associated with food quantity and quality correlated strongly with each other. The higher values of Chlorophyll than pheophytin pigments depict high Chlorophyll rich pigment (Chl/Pheo) and Chlorophyll rich organic matter (Chl a normalized to TOC) representing the freshness of the organic matter while higher pheophytin pigments than chlorophyll decrease Chl/Pheo, Chl a normalized to TOC values and dissolved oxygen. Copepods, polychaetes, nauplius, ostracods abundance increased with increasing concentration of dissolved oxygen. In particularly dissolved oxygen, primarily shaped the meiofaunal assemblage structure. The meiofaunal community structure (density and diversity) showed significant positive correlations with Chl/Pheo and Chl a normalized to TOC. On the other hand, chlorophyll a, pheopigments and organic matter were the secondary factors influencing the meiofaunal assemblage. These results revealed the role of dissolved oxygen in structuring meiofaunal assemblages in the less explored coastal waters off Mumbai and may be useful as a baseline for future comparisons. |