Young scientist maps how animals are responding to decreasing oxygen in NE Pacific Ocean
June 30, 2015

Jackson Chu is a PhD candidate at the University of Victoria who has a passion for seeking answers to the mysteries of the ocean at his doorstep, including how changing oxygen levels affect animals in the ocean. Chu is the lead author on a paper with Dr. Verena Tunnicliffe, professor in Biology and the School of Earth and Ocean Science at the University of Victoria and Canada Research Chair in Deep Ocean Research, which was published in the journal Global Change Biology (April 2015).

“Ocean animals, including those of cultural and economic value, require oxygen to live,” explains Chu, “but oxygen is slowly decreasing from the oceans because of climate change. The west coast of North America is especially a hot spot for expanding hypoxia, or waters that have insufficient oxygen to support life.”

Map of ONC's VENUS observatories in Saanich Inlet.

Chu and Tunnicliffe analyzed over eight years of data from Saanich Inlet, a seasonally hypoxic fjord and home to ONC’s Saanich Inlet ocean observatory. By using remotely operated vehicles (ROVs) equipped with oxygen sensors, they conducted repeat remotely operated vehicle (ROV) surveys over an eight year period of oxygen levels where dozens of fish and invertebrate species, including several commercially important species, are naturally found. Oxygen data delivered on a 24/7 basis over the Internet from ONC’s observatory provided reference oxygen levels.

For a week in early June 2012, the seafloor around the VENUS camera in Saanich Inlet (96m) was alive with squat lobsters

Results show the effect of seasonal oxygen levels

“This is a snapshot of a much bigger problem that is happening all along the west coast,” says biologist Chu. “The expansion of deep-water hypoxia into shallow depths has increased in extent, duration, and frequency over the past several decades. The most hypoxia-sensitive animals in this region will be pushed into the shrinking well-oxygenated part of the ocean—the shallower waters—and competition for limited resources will be increased among all members of the community. The losers of oxygen loss in the oceans will be the bigger, commercially important species, because they require more oxygen.”

Time-series data are vital to long-term understanding

“The Saanich Inlet instrument platform could not have been placed in a better location to resolve the ecology of a system that is experiencing long-term oxygen loss,” says Chu. The ONC oxygen record was not only integral to his research, he adds, but unique in the way it resolved a seasonal hypoxia cycle at extremely high resolution, collecting data every minute.

State of the Ocean data, archived from ONC’s Saanich observatory, reveal temperature, salinity, oxygen and density, over almost ten years.

“This record gave us a rough timeline of when high and low oxygen events occurred in a given year. We used this to plan our ROV surveys at the different phases of the hypoxia cycle, which is another novel aspect of our paper.”

Read the paper: Jackson WF Chu, and Verena Tunnicliffe. "Oxygen limitations on marine animal distributions and the collapse of epibenthic community structure during shoaling hypoxia." Global change biology (2015).

Learn more about Jackson Chu in our Q&A:

Making science happen: a conversation with Jackson Chu, marine biologist

For further information about data, infrastructure and support for biological research such as oxygen time-series/oxygen dynamics/ocean hypoxia on the ONC observatories, please contact: Dr. Richard Dewey.

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