In areas that hardly anyone can see, the ocean is changing. The water is heating up below the sunlit upper layers, far below the depths where most of us think warming really matters. It’s the kind of detail that doesn’t make the evening news, in part because the deep sea has always seemed to be the planet’s quiet basement—far away, chilly, and purportedly unaffected by whatever mayhem is happening on the surface. As it happens, that assumption was wishful thinking.
Nitrosopumilus maritimus, one of the most prevalent microorganisms in the ocean, may be subtly adjusting to all of this, according to a recent study from the University of Illinois Urbana-Champaign and the University of Southern California. Not having any trouble. Changing. And perhaps even flourishing in certain aspects. Researchers believe that this microbe, which is invisible to the naked eye and largely disregarded by the general public, may end up contributing more to ocean chemistry than it currently does. which is noteworthy given how much it already accomplishes.
This class of ammonia-oxidizing archaea makes up about 30% of marine microbial plankton. They are at the base of the nutrient cycle, transforming nitrogen into forms that are essential to the rest of the food chain. The biology of the ocean would not function as it does without them. The phytoplankton would not be able to obtain what they require. It would be felt by fish populations. So would we eventually. It’s the kind of fundamental function that begs the question of why the majority of people are unaware of the organism’s existence.
The way the microbe reacted in the lab is fascinating. Under the direction of Wei Qin and David Hutchins, the team conducted trace-metal-clean experiments, which necessitate meticulous attention to prevent stray iron from contaminating the results, and subjected pure cultures of N. maritimus to a range of temperatures and iron concentrations. The microbe did not fold as the water warmed and iron became more scarce. It continued to function while using less iron and using it more effectively. It has an almost stubborn quality.
One of the main limitations on what microbes can accomplish in large areas of the ocean, particularly the deeper, nutrient-poor zones, has long been thought to be iron limitation. This discovery complicates that picture. Qin stated, “Ocean-warming effects may extend to depths of 1,000 meters or more,” which is the kind of statement that subtly challenges some textbooks. It used to be assumed that the deep remained largely unaware. No longer. Additionally, the consequences for trace metals, particularly iron, are still being worked out.
The picture expanded when Alessandro Tagliabue of the University of Liverpool combined the experimental data with global biogeochemical modeling. Deep-ocean archaeal communities may not simply survive, according to the modeling. In fact, they may increase their control over primary production and nitrogen cycling throughout the vast, iron-starved areas of the world’s oceans. It’s genuinely unclear if that’s good news, neutral news, or something more complex. More nutrient turnover from a more active microbe may have unpredictable upward effects on ecosystems.
Along with twenty other scientists, Qin and Hutchins will board the research ship Sikuliaq later this summer, which will sail from Seattle to the Gulf of Alaska before arriving in Honolulu. The idea is to see if what was demonstrated in the lab holds true in open water. You get the impression that the ocean still has a lot of secrets and that the little things in it could end up being the most significant when you watch a story like this one develop.
