The equatorial Atlantic is among the most biologically productive regions of the global ocean, with surface chlorophyll concentrations showing marked seasonal variability. The annual productivity maximum usually appears as a tongue-shaped band of elevated chlorophyll, primarily during boreal summer. Between 2003 and 2024, no significant long-term trend in chlorophyll concentration was detected in this region, although pronounced interannual variability was observed. The main nutrient sources supporting primary productivity in the equatorial Atlantic are oceanic nutrient transport and atmospheric aerosol deposition. However, their respective contributions to interannual chlorophyll variability remain unclear. To address this question, this study combines satellite remote-sensing observations and reanalysis datasets with correlation analysis, multiple linear regression, and backward-trajectory simulations. The results show that atmospheric aerosols and oceanic nutrient transport contribute 22.4% ± 5.5% and 47.6% ± 11.7% to chlorophyll concentration variability in the equatorial Atlantic, respectively. The principal transport pathway for oceanic nitrate is located between 26°W and 22°W, at depths ranging from 110 to 310 meters. Moreover, under the influence of the subtropical anticyclone, aerosols from North Africa and South America are transported to and deposited over the equatorial Atlantic. These findings provide a scientific basis for quantitatively evaluating the relative roles of atmospheric deposition and oceanic processes in regulating the regional marine ecosystem, and offer important insights into the potential response of the equatorial Atlantic ecosystem to future climate change.

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