What do you think of when someone mentions climate change? Is it polar bears drowning in exhaustion, the ice caps melting, or the increasingly frequent heat waves? Indeed, these are all very real effects of the changing Earth, but something seems missing. If you look at informational pages from official websites like the National Oceanic and Atmospheric Administration, it repeats what you probably already know about the effects of climate change—intensifying droughts, worsening weather, and declining biodiversity. But what about what you don’t know? What’s happening to the things we can’t see–the microorganisms? 

There is an obscene number of microbes on Earth! By estimate, there are roughly 1.2 × 10^30 bacteria and archaea alone, and the vast majority of them inhabit the oceans, which, as we all know, cover the majority of the Earth’s surface. Hence, anything that affects the Earth as a whole will impact the oceans particularly heavily, and climate change is not an exception. 

The rising levels of carbon dioxide in the atmosphere have not only warmed the oceans along with the rest of the planet but also caused them to become more acidic. Compared to preindustrial times, the pH of oceans has decreased by 0.1 units. This sounds insignificant, right? Well, this tiny-seeming amount of change already has “large and negative” effects on everything from the survival to reproduction of marine organisms, as shown by a study that examined and summarized 251 unique previous experiments. By the end of the 21st century, the ocean’s pH is predicted to drop by a further 0.3-0.4 units. 

Microorganisms are part of many biogeochemical cycles crucial to the survival of other species on this planet, like the carbon and nitrogen cycles you may have learned about in high school. Of course, any changes these microorganisms experience can impact these cycles as well–studies on the different groups of microorganisms responsible for each step of the cycles find that some will be diminished while others increase in abundance. This disrupts the delicate cycles, predicting a future where the chemistry of the oceans–and by extension, the entire world–becomes vastly different. 

Besides being affected by it, microorganisms affect climate change as well, making it all the more important to take them into consideration in research and policy-making. Carbon dioxide is a huge factor affecting climate change, and marine phytoplankton perform half of the global photosynthetic carbon dioxide fixation despite only occupying ~1 of the global plant biomass. In addition to phytoplankton, many other groups of microorganisms fix carbon dioxide through ways other than photosynthesis, in dark places like the deep ocean and times like polar winters. 

However, despite their profound importance, bacteria and archaea are never included when the media (even official sources) attempt to educate the public on climate change. These microorganisms are almost never the focus of research on climate change and are also not considered in policy development. Right now, we concern ourselves almost exclusively with issues on land and talk at length about islands and polar bears, completely oblivious to how the basis of all life crumbles and changes in ways beyond our understanding and control, beneath pristine blue waves.