Nutrient regimes control phytoplankton ecophysiology in the South Atlantic

Research reveals that nutrient regimes, particularly iron (Fe) and nitrate availability, significantly control phytoplankton ecophysiology in the South Atlantic. The study, conducted during a GEOTRACES cruise, identified two dominant phytoplankton regimes: one south of the South Subtropical Convergence (SSTC), characterized by elevated chlorophyll concentrations, larger cell sizes, and low photochemical efficiency due to Fe stress; and another north of the SSTC, marked by high photochemical efficiency and macronutrient limitation. Shipboard experiments confirmed that Fe addition mitigated Fe stress, increasing photochemical efficiency in southern waters. Spatial correlations between Fe:nitrate ratios and phytoplankton ecophysiology further supported the role of nutrient supply ratios in shaping these regimes.

Browning, T. J., Bouman, H. A., Moore, C. M., Schlosser, C., Tarran, G. A., Woodward, E. M. S., & Henderson, G. M. (2014). Nutrient regimes control phytoplankton ecophysiology in the South Atlantic. Biogeosciences, 11(2), 463–479. https://doi.org/10.5194/bg-11-463-2014