Mesozooplankton community variability in the Seychelles–Chagos Thermocline Ridge in the western Indian Ocean

• Published in: Journal of marine systems 2022-01, Vol.225, p.103649, Article 103649
• Main Authors: Kim, Minju, Kang, Jung-Hoon, Rho, TaeKeun, Kang, Hyoun-Woo, Kang, Dong-Jin, Park, Jae-Hyoung, Son, Purena
• Format: Article
• Language: English
• Subjects: Epipelagic zone; Mesozooplankton community; Seychelles–Chagos Thermocline Ridge; Water masses; Western Indian Ocean
• ISSN: 0924-7963; 1879-1573
• DOI: 10.1016/j.jmarsys.2021.103649

The Seychelles–Chagos Thermocline Ridge (SCTR), is formed by strong air-ocean interactions that cause open-ocean upwelling in the western Indian Ocean (WIO). The SCTR enhances upper-ocean nutrient levels, which promotes phytoplankton growth, leading to high zooplankton abundance and a strong nursery habitat for fish. To evaluate the evidence of significant upwelling in the SCTR, upwelling indicators associated with variability in the mesozooplankton community and other environmental factors were compared between SCTR and non-SCTR regions. We investigated mesozooplankton and physicochemical factors using multiple opening/closing net and environmental sensing system at three epipelagic (0–200 m) depth strata along 67°E (16°S–5°N) in the central and WIO. Survey stations were clustered into six environmental regions, including SCTR regions (I and II) and non-SCTR regions of the Southwest Monsoon Currents (SMC), Cold-Core Eddy (CCE), and the South Equatorial Current regions North(N) and South(S). Higher abundances of mesozooplankton were observed in the surface mixed layer (SML) (mean: 1275 inds. m−3). In the SML, Noctiluca scintillans were distributed ubiquitously, regions in the CCE were significantly different (p