Neither Plants nor Animals, These Ocean Organisms Protect Their Ecosystems against Heat Waves

Neither Plants nor Animals, These Ocean Organisms Protect Their Ecosystems against Heat Waves

By Ian Rose

For almost two years beginning in 2014, the waters along North America’s Pacific Coast endured the largest and longest-lasting marine heat wave ever recorded. Many species were devastated by ocean temperatures up to 2.4 degrees Celsius (4.3 degrees Fahrenheit) higher than normal. Kelp forests off northern California declined by more than 90 percent, an estimated million or more seabirds died, and fisheries closed up and down the coast, costing some fishing communities hundreds of millions of dollars. But one unassuming group of organisms managed to weather the unrelenting heat fairly well—by breaking the rules of biological separation between animals and plants.

Now new research suggests the flexible lifestyle of these organisms could make them crucial to the survival of ocean ecosystems as climate change continues to crank up the heat.

One of the first things many people learn in biology class is that a basic line can be drawn between two of Earth’s main kinds of life. On one side there are the autotrophs, such as plants, which mostly use photosynthesis to make food out of air, water and minerals, using energy they get from light. On the other are heterotrophs, such as animals, which cannot photosynthesize and so must eat other organisms to get energy. That division is a useful starting point—but like any simplified narrative, it leaves out a lot. All over the world there are organisms called mixotrophs that combine both of these strategies.

On supporting science journalism

If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Various species of mixotrophs form a big part of oceanic plankton and are vital to marine food webs. Mixotrophic plankton such as ciliates and dinoflagellates can get energy by consuming some of the smallest single-celled plankton, which are too tiny to be efficiently used as food by larger species. These mixotrophs can reap the benefits of both photosynthesis and consumption of prey. Some are natural photosynthesizers that supplement…