Response of phytoplankton under varying environmental conditions in Cabo Verde: a seasonal and interannual analysis
Résumé
Abstract Phytoplankton are the foundation of marine ecosystems, yet their response to environmental variability in oligotrophic regions remains insufficiently quantified. This study examines the seasonal and interannual variability of chlorophyll-a (Chl-a) in the Cabo Verde region (1998–2024) and evaluate its relationship with Saharan dust, sea surface temperature (SST), and wind speed. Chl-a displays a double-peaked seasonal cycle, with a primary winter peak (∼0.37 mg·m −3 ) driven by to strong winds and low SST, and a secondary early-summer peak (∼0.40 mg·m −3 ) coinciding with increased dust loading. Principal component analysis reveals a dominant wind–thermal–biological mode explaining 48.55% of the variance, while dust process constitute a secondary, seasonally modulated influence. Dry deposition is positively associated with Chl-a during winter and fall, whereas wet deposition during the summer rainy season coincides with Chl-a minima. ENSO (Niño 3.4) shows a moderate negative correlation with Chl-a in winter ( r ≈ −0.31), while the North Atlantic Oscillation exhibits a moderate positive correlation ( r ≈ +0.28); both relationships are statistically significant ( p < 0.05). These results indicate a consistent, though not very high, association, suggesting that while large-scale climate modes contribute to Chl-a variability, additional factors likely play an important role. Recent warming (2020–2024) reveal strong SST anomalies and suppressed productivity, consistent with stratification-driven nutrient limitation. These integrated findings highlight the dominant role of physical forcing and the conditional influence over of atmospheric inputs on Cabo Verde marine ecosystem.
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