Role of Iron in the Marquesas Island Mass Effect

A significant phytoplankton bloom, known as the Marquesas Island Mass Effect, occurs at the boundary between equatorial mesotrophic and subtropical oligotrophic waters in the central South Pacific Ocean. This phenomenon is characterized by high chlorophyll-a concentrations, a proxy for phytoplankton biomass, despite iron depletion in the surrounding waters. Through modeling simulations with varying iron sources, researchers found that iron input from island sediments is crucial in replicating observed patterns of chlorophyll distribution, though the simulated effect was weaker than real-world observations. The study also highlights the importance of remote processes, such as horizontal advection and vertical mixing, in modulating seasonal phytoplankton dynamics around the Marquesas archipelago by transporting nutrient-rich waters from the equator.

Raapoto, H., Martinez, E., Petrenko, A., Doglioli, A., Gorgues, T., Sauzède, R., Maamaatuaiahutapu, K., Maes, C., Menkes, C., & Lefèvre, J. (2019). Role of Iron in the Marquesas Island Mass Effect. Journal of Geophysical Research: Oceans, 124(11), 7781–7796. Portico. https://doi.org/10.1029/2019jc015275