MIT Study Suggests Long-Sought Dream Of Iron Fertilization Of Oceans Would Flop

[hatrack]

EDIT

According to Lauderdale, the impacts of iron fertilization in a dynamic ocean ecosystem are much less straightforward than those Martin saw in his bottles. “Over the last 20 or 30 years, we’ve gotten a much better idea of how interconnected the ocean is,” he said. For instance, the excess nutrients that are not consumed by phytoplankton in the Southern Ocean “get folded into the ocean circulation, and they outcrop in more dusty regions where there’s lots of iron,” he said; the process provides around 75% of the nutrients that feed phytoplankton growth in the northern oceans.

It’s not a one-way relationship either, the researchers found by simulating the mineral concentrations and circulation patterns found in different parts of the ocean to investigate the interplay of microbes, iron and other nutrients. Phytoplankton have evolved the ability to produce organic molecules called ligands, which make iron more bioavailable. The researchers found that ligands secreted by phytoplankton in the North Atlantic carry iron as they ride currents back into the Southern Ocean to feed the phytoplankton there. “The microbes have this ability to tune the marine chemistry for their own purposes,” Lauderdale said, “and so they’ve engineered this system to be optimal for themselves.

“But eventually, they’re going to run out of something else,” he said — other nutrients or sufficient sunlight to support a bigger population, for instance. “And so that feedback mechanism, in our models and in our hypothesis, matches the availability of iron to the other resources that the phytoplankton need to grow.” That means adding iron to the Southern Ocean to stimulate plankton growth will reduce the amount of macronutrients being delivered to the North Atlantic, which will affect the productivity of phytoplankton there — and may actually reduce the amount of bioavailable iron in the Southern Ocean, too, in the longer term. “So the net effect of that is zero,” Lauderdale said.

What’s more, phytoplankton sit at the base of the marine food chain, so interfering with their populations would significantly impact marine ecosystems — particularly in the North Atlantic, where millions of people depend on fisheries for their livelihoods. Some experiments have also shown that fertilization favors certain kinds of phytoplankton over others, so the process could cause toxic algal blooms and deoxygenate water, depleting marine life. Concerns over this possibility led the United Nations Convention on Biological Diversity to establish a moratorium on all ocean-fertilization projects in 2008, apart from small-scale, coastal experiments.

EDIT

https://news.mongabay.com/2020/03/climate-fix-fertilizing-oceans-with-iron-unlikely-to-sequester-more-carbon/

[Xipe Totec]

1. Bummer. nt