No Fad Diets For Beetles

Here’s a set of articles on iron fertilization science by a science writer named Hugh Powell (he wrote parts 1-5). I worked for Hugh when he was a field biologist in western Montana, studying the dietary peculiarities of the Black-backed Woodpecker by picking through piles of bark to count and identify wood-boring beetle larvae by the hundreds. Those were great field experiences. The subject he’s writing on here is a topic that I cover in the ecosystem ecology course that I teach. Hugh has been writing in several places, apparently, including this nice blog here, and over here for the smithsonian magazine. Good work, Hugh!

Under different circumstances, and for different organisms, different nutrients limit the growth of individuals and hence populations. Iron is an important cofactor in the enzymes of organisms, and it can be a growth-limiting element for plankton in the open oceans. These areas are iron-limited because they are too far from continents for significant amounts of iron-rich dusts to reach and there is little upwelling of nutrient-rich waters from the deep ocean.

Why should we care about the iron limitation of microorganisms out in the middle of the ocean? Some scientists have suggested that relieving the iron deficit will stimulate phytoplankton blooms and solve, in part, the human caused atmospheric increases of the greenhouse gas carbon dioxide. Phytoplankton are carbon-fixing photosynthesizers that sink deeper into the ocean after they die. If phytoplankton productivity is stimulated by the addition of iron, more carbon should be pulled from the atmosphere into the ocean and sunk in the bodies of the plankton. Thus, on a large scale, iron fertilization could remove greenhouse gases enough to mitigate the climate. Unfortunately, most of the productivity in the phytoplankton is consumed by other organisms (bacteria and zooplankton) that respire carbon dioxide, so the climate mitigation strategy isn’t extremely efficient at this stage. The state of the science is to find out how to increase the efficiency of sinking that carbon. Read Hugh’s articles for much more detail.