Understanding the Role of Nutrient Limitation on Plankton Biomass Over Arabian Sea Via 1‐D Coupled Biogeochemical Model and Bio‐Argo Observations

Abstract

Arabian Sea (AS) is known to have seasonal phytoplankton blooms during winter and summer driven by dynamically distinct physical forcing mechanisms and associated nutrient dynamics. A 1‐D coupled physical‐biogeochemical model based on North Pacific Ecosystem Model for Understanding Regional Oceanography (NEMURO) with nitrogen and silicon cycles is adapted for the AS environment. The model is implemented to investigate the role of nitrogen (nitrate + ammonium) versus silicate limitation on plankton biomass. The seasonal cycle of plankton biomass is well simulated by the model along bio‐Argo (during a period from 2013 to 2016) and ship cruise tracks (for the single year 2009). Further, three sensitivity simulations are conducted by suppressing (1) nitrate availability (representing new production), (2) ammonium availability (representing regenerated production), and (3) silicate availability (for diatom production). The new production represents 80% of the total primary production in the AS and implicitly controls 70% of total zooplankton production annually. The regenerated production augments small phytoplankton (by ~50%; e.g., flagellates) and small zooplankton (by ~20%; e.g., ciliates) growth with negligible effects on large phytoplankton (e.g., diatom) and predatory zooplankton (e.g., copepods). The diatom production remains within the observed range due to silicate limitation which is fundamental in the model for realistic simulation of chlorophyll. Silicate is the primary limiting nutrient in diatom bloom in the subsurface chlorophyll maxima with maximum limitation occurring during the winter season, due to the deeper silicicline as compared to shallower nitricline. At the surface, both nitrogen and silicate co‐limit the total production; however, nitrogen is a stronger limiter than silicate from March to June. The study highlights the relative role of silicate versus total nitrogen (nitrate + ammonium) in limiting primary production in the AS.

Evaluation of Clove Phytochemicals as Potential Antiviral Drug Candidates Targeting SARS-CoV-2 Main Protease: Computational Docking, Molecular Dynamics Simulation, and Pharmacokinetic Profiling

“…Despite fast-tracking the research of COVID cure, no potential lead molecules that can effectively break the viral proliferation chain within an individual are identified ( Anju et al, 2020 ). Moreover, many studies are performed on phytochemicals from medicinal plants for their efficacy against the current COVID-19 disease.…”

Impact of atmospheric anthropogenic nitrogen on new production in the northern Indian Ocean: constrained based on satellite aerosol optical depth and particulate nitrogen levels

“…8,[34][35][36]63 Severe nitrogen limitation to primary production was reported in the northern Indian Ocean. 26,27,68 Assuming that the deposited inorganic nitrogen (nitrate and ammonium) on the surface ocean is completely utilized by the phytoplankton, it may support a primary production of 0-18.5 mg C m À2 day À1 in the northern Indian Ocean (Fig. 9b and c).…”

“…20,21 Seasonal reversal of the wind pattern 22 leads to variability in the sources and composition of aerosols over the north Indian Ocean (NIO). 14,[23][24][25] Nitrogen is reported to be one of the severe limiting nutrients in the NIO 26,27 resulting in the xation of atmospheric nitrogen. [28][29][30][31] An increase in primary production and phytoplankton community change due to the deposition of atmospheric nutrients were reported in the Bay of Bengal.…”

Surface pH Record (1990–2013) of the Arabian Sea From Boron Isotopes of Lakshadweep Corals—Trend, Variability, and Control

“…Based on this multi‐proxy approach (δ 11 B [pH], δ 13 C [calcification processes], Sr/Ca and Li/Mg [SST]), we have investigated the roles of regional oceanographic processes vis‐à‐vis anthropogenic CO 2 forcing in modulating surface ocean pH variability in the Arabian Sea. The north‐western Indian Ocean is influenced by wind‐driven upwelling and vertical mixing that affects the surface ocean circulation, convection, nutrients supply and productivity (Anju et al., 2020; K. Chakraborty et al., 2018; Lévy et al., 2007). Therefore, a regional pH reconstruction from the Lakshadweep would provide a better insight into the resilience of the corals growing under large variability in physical and biological processes in a strong upwelling region of the tropical oceans.…”

“…Based on this multi-proxy approach (δ 11 B [pH], δ 13 C [calcification processes], Sr/Ca and Li/Mg [SST]), we have investigated the roles of regional oceanographic processes vis-à-vis anthropogenic CO 2 forcing in modulating surface ocean pH variability in the Arabian Sea. The north-western Indian Ocean is influenced by wind-driven upwelling and vertical mixing that affects the surface ocean circulation, convection, nutrients supply and productivity (Anju et al, 2020;K. Chakraborty et al, 2018;Lévy et al, 2007).…”