Lower Ocean Oxygen Levels May Dramatically Alter Ecosystems

A new study published in Science Advances finds just the slightest change in oxygen level could have tremendous ramifications on the food chain.

The rising temperatures of the oceans are causing mid-water regions with low oxygen levels, known as the Oxygen Minimum Zones (OMZs), to expand in the eastern tropical North Pacific Ocean. The study found that while some organisms in certain regions may be able to adapt, the majority of species living in the expanded OMZ’s likely die or have to find a new home as oxygen levels will be too low.

“These animals have evolved a tremendous ability to extract and use the small amount of oxygen available in their environment,” said study author Brad Seibel, Ph.D., professor of biological oceanography at the University of South Florida College of Marine Science. “Even so, we found that natural reductions in oxygen levels of less than 1% were sufficient to exclude most species or alter their distribution.”

The research was performed by looking at different types of marine zooplankton as well as fish and crustaceans that are pivotal to the marine food chain. An example of a species that will be greatly impacted are the krill which act as a backbone to the food oceans food chain.

While we will see an expansion of the OMZ, species that will have to adapt will likely travel to shallower waters where they will face more sunlight, higher temperatures and a greater risk of predators.

The researchers in the study found that the animals that did live in this region had a tremendous tolerance for low oxygen but the species were reaching the their evolutionary limit and further oxygen changes will dramatically alter the ecosystems.

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