Impacts of coastal upwelling Iron limitation in the Humboldt Current 

LAOCA Co-chair Dr. Victor Aguilera recently co-authored a study published in the  Journal of Sea Research entitled “Nearshore iron limitation in the Humboldt Current  and potential impacts on toxicity and grazers”. The southeastern Pacific upwelling  system, one of the world's most productive marine ecosystems, supports valuable  ecosystem services, including fisheries, aquaculture, carbon sequestration, and the  maintenance of marine biodiversity. Despite the high availability of macronutrients  supplied by coastal upwelling, this study demonstrates that phytoplankton growth  can be constrained by iron supply in nearshore waters of the Humboldt Current.  Experimental iron additions stimulated phytoplankton biomass and altered  community responses, revealing that iron limitation can occur even in productive  coastal environments traditionally considered nutrient-rich. Furthermore, iron  enrichment increased domoic acid production by toxigenic diatoms, highlighting that  variations in micronutrient supply may influence not only primary productivity but also  food-web quality and the occurrence of harmful algal blooms with potential impacts  on marine wildlife, fisheries, and human health. These findings have broader  implications under ongoing climate change. Because central-northern Chile is  experiencing persistent megadrought conditions and increasing exposure of  unvegetated soils, atmospheric dust may become an increasingly important vector of  iron toward the coastal ocean, where the Chilean scallop (Argopecten purpuratus)  aquaculture industry is concentrated. Atmospheric dust has the potential to locally  alleviate iron limitation in surface waters. Consequently, future changes in dust  emissions and wind regimes may modify coastal productivity, phytoplankton  community structure, and toxin production. Although the present study did not  directly evaluate atmospheric iron deposition, it identifies iron supply as a key  regulator of ecosystem functioning, supporting the hypothesis that increased aeolian  iron inputs during drought conditions could become an important driver of biological  responses in the coastal Humboldt Current ecosystem. 

Figure 1. A) DA levels in microcosms from Sites 2S and 2N. Microcosm pairs are  indicated by lines. B) The pairwise normalized difference in DA vs difference in  Fv/Fm. Lines represent linear regression with 95% confidence interval (R2 =  0.60, p = 0.024). 

Reference:

Von Dassow, P., Aguilera, V. M., Torres, R., Alves-de-Souza, C., Auger, P. A., Broitman,  B. R., & Krock, B. (2026). Nearshore iron limitation in the Humboldt Current and  potential impacts on toxicity and grazers. Journal of Sea Research, 102709. https://doi.org/10.1016/j.seares.2026.102709

(Summary submitted by the author Víctor M. Aguilera.)