A Tiny Plant That Feeds the Oceans’ Biggest Creatures Could Be Wiped Out by Climate Change

Researchers say the world’s acidifying oceans threaten the survival of phytoplankton, microscopic organisms that support nearly all marine life.
(Photo: Maxi Jonas/Reuters)
Jul 22, 2015· 1 MIN READ
David Kirby has been a professional journalist for 25 years. His third book, Death at Seaworld, was published in 2012.

Imagine if climate change wiped out humans’ main source of food on land. That’s what’s happening in the world’s oceans as they absorb increasing amounts of carbon dioxide from the burning of fossil fuels. Growing acidification threatens to kill off whole species of phytoplankton, microscopic ocean plants that support nearly all marine life, according to a new study.

“I was alarmed,” said Stephanie Dutkiewicz, the study’s lead author and a principal research scientist at MIT's Center for Global Change Science. “We might see some very traumatic changes in these communities during the 21st century.”

So, Why Should You Care? Phytoplankton live near the ocean’s surface and are the fundamental building blocks for the entire marine food chain, including dolphins, seals, and polar bears. Many species of whales, shrimp, snails, and jellyfish depend directly on the plankton for survival.

“Phytoplankton are really important in many ways,” Dutkiewicz said. “They’re the base of the food web, so anytime you eat anything that comes out of the ocean, whether it’s a fish or a lobster, it ate something that ate something” that ate phytoplankton.

Consider this: These tiny plants not only feed the oceans but help the world to breathe.

“Every time you take a breath,” Dutkiewicz said, “about half of that oxygen comes from phytoplankton.”

Oceans around the world absorb up to 30 percent of human-generated carbon dioxide, according to the study. As CO2 levels increased over the past 100 years, so did ocean acidity. According to the MIT researchers, average ocean pH has fallen from 8.2 in preindustrial times to 8.1 today, and it could reach 7.8 by 2100. Lower pH means higher acidity.

Phytoplankton that can survive or even thrive in more acidic water will have an increasing competitive advantage over those that cannot, said Dutkiewicz.

Dutkiewicz and her team reviewed data from 154 experiments in 49 studies on how individual phytoplankton species survived at lower pH levels. They then plugged those findings into a global ocean circulation model to determine how various species would compete with one another as water acidity rises.

“Some increased growth, and some died out,” Dutkiewicz said, adding that certain marine species feed only on certain phytoplankton and would be severely affected if those communities disappeared.

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An overabundance of acid-resistant phytoplankton, meanwhile, could have its own serious consequences, though that question was beyond the scope of the study, Dutkiewicz said.

Ingrid Biedron, a marine scientist at the nonprofit group Oceana, said individuals can help save the oceans.

“In your daily life, you can help slow ocean acidification by lowering your carbon and nutrient output levels,” Biedron said in an email. “Examples of how to do this include using energy-efficient transportation, buying compact fluorescent light bulbs, doing a home energy audit, and decreasing how much food you waste.”