MAR 19, 2020 1:36 PM PDT

What's the Ocean's Oxygen Budget?

WRITTEN BY: Tiffany Dazet

Have you heard the statement, “every other breath you take comes from the ocean?” Oxygen-producing phytoplankton are just one part of the oxygen transactions taking place in the sea. The video below summarizes the ocean’s oxygen services, as well as recent research from Woods Hole Oceanographic Institution (WHOI).

The above video compares oxygen to “money for the earth.” It states that oxygen deposits are made in three essential ocean layers: with surface air, in the water from photosynthesizing phytoplankton, and the seafloor with plants and corals. Oxygen withdrawals occur when various organisms consume oxygen.

The video is based on research from Matthew Long, WHOI scientist of marine chemistry and geochemistry. Long developed instruments to measure oxygen throughout ocean layers, which were deployed in two shallow-water habitats, a reef and an eelgrass bed, to understand more about the ocean’s oxygen budget. Two research papers produced on this topic were published last year in Limnology and Oceanography.

At the reef site, Long and the research team discovered that oxygen measurements changed throughout the day. During daylight hours, oxygen was abundant. However, at night oxygen levels were lower or “withdrawn” using the bank metaphor. Researchers observed the same pattern at the eelgrass beds, although with ten times more oxygen than at the reef site. The team suggests that because the eelgrass bed was at a shallower depth, it could produce more oxygen than the reef.

Additionally, changing tides impacted oxygen levels in the seagrass bed. The water was so oxygen-rich at the high noon low tide that bubbles were visible in the water. Bubbles that reached the surface deposited oxygen into surface air through a process called ebullition. To measure how much oxygen released to surface air through ebullition, the team used a bubble trap. When the tide rose and daylight faded, oxygen production slowed. However, organisms in the seagrass bed continued to consume oxygen, resulting in hypoxic conditions.

The instruments used in this study can be used to examine the oxygen budget of various ocean ecosystems. Because oxygen is a critical component of ocean and ecosystem health, it is crucial to understand how oxygen is being created and used. The WHOI team believes that creating an ocean oxygen budget will help scientists understand more about ecosystem dynamics such as primary production, carbon storage, ocean acidification, and hypoxia.

Sources: WHOI, Limnology and Oceanography (1), Limnology and Oceanography (2)

About the Author
Bachelor's (BA/BS/Other)
Tiffany grew up in Southern California, where she attended San Diego State University. She graduated with a degree in Biology with a marine emphasis, thanks to her love of the ocean and wildlife. With 13 years of science writing under her belt, she now works as a freelance writer in the Pacific Northwest.
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