Can phytoplankton growth be stimulated in oceans to sequester CO2?

Question

Casual learner only. Decades ago, I read, one ocean scientist stated, jokingly, probably, "Give me half a shipload of iron filings and I will give you another ice age." This was in response to the fact of iron being the only deficit in the southern ocean holding back phytoplankton growth. Some experiments did take place since then revealing a danger of toxic blooms and that the iron did not stay long enough in the upper ocean to have significant effect. But I find no continued investigations into stimulating phytoplankton growth despite it being such a major source of carbon absorption.

Answer 1

Research into the topic has been intermittent for a variety of reasons. Ocean iron fertilization experiments – past, present, and future looking to a future Korean Iron Fertilization Experiment in the Southern Ocean (KIFES) project reviewed the status of research on the topic in 2018 and recommended ways the concept could be tested.

The "iron hypothesis" put forth by John Martin in 1990 was that iron dust carried into the ocean accelerated historic ice ages by fertilizing phytoplankton which then captured enormous volumes of carbon dioxide, reducing the greenhouse effect -- iron being a key nutrient for phytoplankton. The suggestion followed that one could combat modern global warming by artificially fertilizing oceans with iron filings.

The KIFES paper linked above and other sources suggest no credible scientific organization has wanted to conduct the large-scale experimentation and risk the potential ecological impacts and public disapproval to test out whether iron fertilization will have the desired sequestration effects, though some startups such as Blue Dot Change plan to try on their own, according to MIT Technology Review.