WHOI Study Reveals the Hidden Molecules That Drive the Ocean’s Carbon Cycle

The surface waters that boaters, anglers, and coastal communities depend on are teeming with invisible chemical exchanges that help regulate Earth’s climate. A new study led by Woods Hole Oceanographic Institution and Columbia University has identified the specific molecules that marine phytoplankton release into seawater — compounds that fuel microbial life and power the ocean’s massive carbon cycle. For anyone who spends time on the water, this research underscores just how much vital chemistry is happening in every gallon of ocean beneath the hull.

As WHOI reports:

Phytoplankton, a type of microscopic organism, take in carbon dioxide and convert it into organic carbon through photosynthesis, like plants. Each year, this process moves many tens of billions of tons of carbon through the sunlit surface ocean and contributes to the oxygen in the air we breathe. These massive natural carbon flows highlight the central role the surface ocean plays in regulating Earth’s carbon cycle.

“For this study, we placed six phytoplankton species representing major groups of marine phytoplankton under controlled conditions. They had the nutrients and light they needed to grow,” said Yuting Zhu, co-lead author of the study. “Using a chemical-tagging method developed at WHOI, we were able to quantify the composition of biologically available small molecules released by globally abundant microorganisms.”

The researchers found that these compounds accounted for up to 23 percent of the dissolved organic carbon that phytoplankton released, and that different phytoplankton species produce distinct chemical “menus” — which in turn determine which bacterial communities thrive in different ocean regions. The study was conducted as part of the NSF-funded Center for Chemical Currencies of a Microbial Planet, with future research planned to examine how warming temperatures and ocean acidification may alter these critical microbial exchanges.