Estudo da distribuição de nutrientes (Ferro, Nitrato e Fosfato) e sua relação com a produtividade primária na região norte e centro do Canal de Moçambique

Abstract

The present study aims to examine the distribution of nutrients (Fe, NO₃⁻, and PO₄³⁻) and their relationship with primary productivity in the Northern and Central regions of the Mozambique Channel. For this purpose, biogeochemical data (Fe, NO₃⁻, PO₄³⁻, and NPPV) available from the CMEMS (Copernicus Marine Environmental Monitoring Service) were analyzed through simulations using the BIORYS numerical model, covering a three-year period from 2020 to 2022. The results revealed strong seasonality in both highlighted regions for the four parameters analyzed. In general, higher concentrations of nutrients and NPPV were observed in winter and lower in summer, except for PO₄³⁻, which showed an opposite trend. A non-linear relationship between nutrients and NPPV was observed. In the northern, the highest peaks of NPPV occurred in September and October (~10 mgC/m³/h), while Fe peaks occurred in June and September (~12x10⁴ µmol/m³), resulting in a weak negative linear correlation between Fe and NPPV (r = -0.42). The relationship between NO₃⁻ and NPPV showed a strong positive linear correlation (r = 0.80), with NO₃⁻ peaks in September, December, and December (~0.03 µmol/m³, 0.02 µmol/m³, 0.01 µmol/m³), coinciding with NPPV peaks. The variation of PO₄³⁻ and NPPV also showed oscillations, with a null positive linear correlation (r = 0.20). The highest peaks of PO₄³⁻ occurred in January, February, and December (~0.2 µmol/m³, 0.15 µmol/m³, 0.2 µmol/m³), coinciding with the highest peaks of NPPV. In the Central region, the highest peaks of Fe occurred in March, May, and June (~2.5 µmol/m³), coinciding with the highest peaks of NPPV in March, April, and November (~28 mgC/m³/h, 25 mgC/m³/h, 20 mgC/m³/h), with a moderate positive linear correlation (r = 0.66). On the other hand, the variation between NO₃⁻ and NPPV showed a high positive correlation (r = 0.75), with NO₃⁻ peaks in March and May (~2.5 µmol/m³), coinciding with NPPV peaks in the same months. The variation of PO₄³⁻ and NPPV revealed PO₄³⁻ peaks in October, May, and December (~0.1 µmol/m³, 0.1 µmol/m³, 0.12 µmol/m³), coinciding with NPPV peaks in March, April, and November (~28 mgC/m³/h, 28 mgC/m³/h, 20 mgC/m³/h), with a null negative linear correlation (r = -0.18). The study demonstrated that the spatial distribution of nutrients influences primary productivity in the Northern and Central regions of the Mozambique Channel.