Toxic impact of aluminium on the natural phytoplankton community during spring in the Atlantic sector of the Southern Ocean

Abstract

The natural Southern Ocean phytoplankton community plays a pivotal role in both the marine trophic chain and global climate regulation. Previous studies and models have primarily focused on the individual effects of iron (Fe) on phytoplankton, often overlooking the potential toxic impact of aluminium (Al) and its interactive effects with Fe and cobalt (Co). Here, a series of controlled incubations involving the addition of trace metals (Al, Fe, and Co) were conducted to evaluate the potential effects of these elements in the Polar Frontal Zone and the Marginal Ice Zone. The findings revealed that the introduction of 1 nM of Al prompted a reduction in biomass of the entire natural community, coupled with a decrease in the photosynthetic efficiency (F_v/F_m) and an increase of the absorption cross-section of photosystem II (σ_PSII). A similar toxic impact of Al addition was observed at both sites, however, the level of cell activity and presence of other micronutrients (Fe, Co) attenuated the toxicity to some extent. Despite its connotations, Al toxicity is not considered an immediate threat to the sub-Antarctic phytoplankton community, however, the scenario could differ in regions where increased lithogenic input is likely.