Effect of high level iron enrichment on potential nitrogen uptake by marine plankton in the Southern Ocean

Abstract

Iron fertilization of the Southern Ocean is believed to counter the increasing CO₂ concentration in the atmosphere and the consequent global warming. Though a number of large scale iron enrichment experiments have been done in the recent past in different parts of the world ocean, little effort has been made to understand the effect of iron enrichment on nitrogen uptake rates and f-ratios. Here we assess the effect of iron addition on N-uptake rates and f-ratio in the Indian sector of the Southern Ocean. This study shows, in contrast to the earlier belief, that iron addition enhances not only nitrate uptake (~ 3×) but it causes a significant increase in ammonium (~ 2×) and urea (~ 3×) uptakes as well. Also, since iron enrichment caused significant increase in the uptake of all N-substrates, its effect on f-ratio was insignificant.