Climate Change Is Transforming the Chemical Properties of Plankton, Threatening Fisheries and Growing Dead Zones

Climate change is leaving no stone untouched in its never-ending quest to screw everything up. Not content with its marquee disasters—the heat waves, the drought, the floods—global warming has moved on to a bunch of other less predictable woes. Like, opening up new vectors for infectious diseases, messing with animals' migratory patterns, and, now, picking on plankton. Which is a lot more serious than it might sound at first.

A new study published in Nature Climate Change shows that warming waters are likely to start screwing with the plankton and micro-algae that are crucial to sustaining our oceans. It turns out those billions of tiny, invaluable creatures are more vulnerable to temperature shifts than previously thought. And that's bad news in our fast-warming world.

"Our new data add to concerns about the effect of global warming on marine ecosystem functioning," Dr. Thomas Mock, the study's lead author, wrote me in an email. As if there wasn't enough concern, what with ocean acidification, coral bleaching, and so on.

“Phytoplankton, including micro-algae, are responsible for half of the carbon dioxide that is naturally removed from the atmosphere," Mock said. "As well as being vital to climate control, it also creates enough oxygen for every other breath we take, and forms the base of the food chain for fisheries so it is incredibly important for food security."

In other words, phytoplankton prop up the air we breathe and the fish we eat. Unfortunately, they're kind of touchy about room temperature. Using a sophisticated computer model that "took into account world ocean temperatures, 1.5 million plankton DNA sequences taken from samples, and biochemical data," they discovered that warmer water temperatures actually transform the microscopic plankton's chemical properties.

“We found that temperature plays a critical role in driving the cycling of chemicals in marine micro-algae," Mock said. "It affects these reactions as much as nutrients and light, which was not known before." Temperature, it turns out, has a profound influence on how these little blue-green guys work. And it's all about the ribosomes.

"Under warmer temperatures, marine micro-algae do not seem to produce as many ribosomes as under lower temperatures. Ribosomes join up the building blocks of proteins in cells. They are rich in phosphorous and if they are being reduced, this will produce higher ratios of nitrogen compared to phosphorous, increasing the demand for nitrogen in the oceans."

Big deal, right? BUT. “This will eventually lead to a greater prevalence of blue-green algae called cyanobacteria which fix atmospheric nitrogen."

Okay, that might not sound like much either. BUT. It could have dire consequences for all of the non-cyanobacteria life that happens to live out there. For one thing, the ensuing boom of hungry cyanobacteria might overwhelm the diverse, larger algae, and deprive fish of a vital food source (the blue-green algae isn't as good for eating). The lack of fish, of course, would then deprive millions of humans of a vital food source, too.

Furthermore, in tropical areas, a rise in cyanobacteria could lead to more ocean dead zones "if they would be able to build up a lot of biomass (large blooms) in surface waters that would sink down to the bottom of the ocean," Mock says. "Something like that has been observed in the Baltic Sea but not so often in the open ocean."

Dead zones are currently a scourge in places like the Gulf of Mexico, where a New Jersey-sized area is being sapped of oxygen by the rabid cyanobacteria—literally nothing else can survive, these guys are so crazed for oxygen.

As with so many of these alarming climate impacts, we can't be sure just how they'll shake out. But the prospect of afflicted plankton, dwindling fisheries, and growing dead zones in our heating oceans are grim ones indeed.