Factors Controlling the Lack of Phytoplankton Biomass in Naturally Iron Fertilized Waters Near Heard and McDonald Islands in the Southern Ocean

Despite high natural iron fertilization from glacial and volcanic sources near Heard and McDonald Islands, phytoplankton biomass remains unexpectedly low compared to the central Kerguelen Plateau. This paradoxical 'high nutrient, high iron, low chlorophyll' (HNHFeLC) phenomenon was investigated using ocean color data and in situ samples collected during the HEOBI voyage in 2016. Researchers found that deep mixing, shading by re-suspended sediment particles, and dilution with surrounding low-chlorophyll waters in the Antarctic Circumpolar Current played significant roles in limiting phytoplankton growth. Additionally, a shift from microphytoplankton to nanophytoplankton dominance was observed, highlighting the complex dynamics of short-term responses to climate change and cryospheric processes.

Wojtasiewicz, B., Trull, T. W., Clementson, L., Davies, D. M., Patten, N. L., Schallenberg, C., & Hardman-Mountford, N. J. (2019). Factors Controlling the Lack of Phytoplankton Biomass in Naturally Iron Fertilized Waters Near Heard and McDonald Islands in the Southern Ocean. Frontiers in Marine Science, 6. https://doi.org/10.3389/fmars.2019.00531