"Our study provides a perspective on the monitoring of oxygen decline in the ocean from a different angle," says principal investigator Daniele Daffonchio."Oceanic systems have a natural mechanism for regulating oxygen dissolution by balancing oxygen-consuming and oxygen-producing processes."
Current models fail to project oxygen dynamics of coastal ecosystems that have an abundance of organisms that photosynthesize, says marine scientist Marco Fusi, who led the study with Folco Giomi from the University of Padova, Italy. Examples include seagrass meadows,and coral reefs."It's a very different dynamic from what's seen in unproductive parts of the ocean in some cases called the 'blue desert,'" he says.
In an initial observation of crabs in a mangrove forest, Fusi found they could survive in waters reaching over 40 degrees, well above their known thermal threshold. The waters were"oxygen-supersaturated," a state in which more oxygen was dissolved in the water than would be through equilibrium with the atmosphere. This extra oxygen production due to warmer temperatures was helping the crustaceans cope.
The researchers also discuss fluctuations in the Venice Lagoon, once considered one of the most oxygen-depleted"dead zones" in the Adriatic Sea. The lagoon hosts a complex mosaic of ecosystems that include seagrasses and salt marshes colonized by microalgae and cyanobacteria. While dissolved oxygen was low at night, the lagoon reached nearly 300 percent saturation during the day.
Data from coral reefs in the Red Sea—formerly regarded a low oxygen zone due to high temperatures—shows a similar pattern."The marine species in these areas are accustomed to living in a rollercoaster ofThe team advises that conservation management should be based not on linear models focusing on average values of"Predictions of biodiversity loss in the Red Sea from two decades ago indicated that 90 percent of biodiversity would have been lost by now. That hasn't happened yet.