Navigation Links
Ocean's most oxygen-deprived zones to shrink under climate change
Date:8/7/2014

As the complex story of climate change unfolds, many of the endings are grim. But there are exceptions. Predictions that the lowest-oxygen environments in the ocean would get worse may not come to pass. Instead, University of Washington research shows climate change, as it weakens the trade winds, could shrink the size of these extreme low-oxygen waters.

"The tropics should actually get better oxygenated as the climate warms up," said Curtis Deutsch, a UW associate professor of oceanography. He is lead author of the study published Aug. 8 in Science.

Warmer water contains less gas, so climate change is expected to reduce oxygen levels worldwide. Observations show this is already taking place in many places. Declines during the past 20 years in the tropical low-oxygen zones, the lowest-oxygen waters on the planet, had led to a 2008 study proposing that these zones would also get worse over time.

Tropical regions are usually associated with an abundance of life, but they have some of the most inhospitable places for ocean dwellers. The oxygen minimum zones off Mexico and Peru have oxygen levels already too low to support most animals (so, unlike in other low-oxygen zones, here there's no risk of killing fish).

But when those levels drop even further, a particular group of bacteria, which can use nitrogen instead of oxygen as a source of energy, thrive. Nitrogen is an essential and very scarce nutrient for marine plants. When oxygen levels get low enough for that particular group of bacteria to take over, significant amounts of the ocean's fertilizer get deep-sixed to the bottom of the tropical ocean.

The new paper shows that water flowing into the tropics is indeed likely to get lower in oxygen, decreasing the initial oxygen supply. But demand will also shift under climate change. Specifically, as the trade winds weaken, the whole sequence of events that feeds this bacterial food chain will slow down, and the low-oxygen zone will shrink.

"If we want to understand how biological and chemical aspects of the ocean will change in the future, we really have to pay a lot of attention to what happens with the winds," Deutsch said. "The winds can lead to conclusions that are exactly the opposite of what you'd expect."

Trade winds from the west cause deep water to percolate up along western coasts, bringing nutrients up from the deep sea. These nutrients feed marine plants, which feed marine animals, which decompose to feed bacteria that use up the remaining oxygen. As trade winds weaken, less nutrient-rich water percolates up from the deep. Fewer plants grow at the surface. Finally, fewer oxygen-gobbling bacteria can survive.

Deutsch is a climate modeler who studies tropical ocean circulation. He learned of sediment cores, collected off Mexico by co-authors William Berelson at the University of Southern California and Alexander van Geen at Columbia University, that showed a puzzling longer-term trend. The authors worked together to interpret the samples. Results show that for most of the time since 1850 the population of these nitrogen-eating bacteria has been going down, coincident with warming oceans and weakening trade winds. This implies that the local oxygen levels, for which few direct measurements exist, have been rising.

"I find it an interesting question for understanding the way the ocean functions on climatic or geologic timescales," Deutsch said.

Most climate models predict that trade winds will continue to weaken in the future, shrinking the oxygen-minimum zones in the Pacific Ocean off the coasts of Mexico, Chile and Peru, and in the Indian Ocean off western Australia.

Decreasing oxygen in the wider ocean is still a major concern, Deutsch said, as are overfishing, ocean acidification and warming water temperatures. "This study shows that what happens to the winds, which is sometimes overlooked, is really important for predicting how the oceans will respond to climate change," Deutsch said.


'/>"/>

Contact: Hannah Hickey
hickeyh@uw.edu
206-543-2580
University of Washington
Source:Eurekalert

Related biology news :

1. Calcification in changing oceans explored in special issue of The Biological Bulletin
2. SAR11, oceans most abundant organism, has ability to create methane
3. Can coral save our oceans?
4. Warming climates intensify greenhouse gas given out by oceans
5. Metabolism may have started in our early oceans before the origin of life
6. Fish living near the equator will not thrive in the warmer oceans of the future
7. New studies needed to predict how marine organisms may adapt to the futures acidic oceans
8. Scientists reveal why life got big in the Earths early oceans
9. UCLA report urges new global policy effort to tackle crisis of plastic litter in oceans
10. Coral chemicals protect against warming oceans
11. Glimpse into the future of acidic oceans shows ecosystems transformed
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/19/2016)... 2016 The new GEZE SecuLogic ... web-based "all-in-one" system solution for all door components. It ... the door interface with integration authorization management system, and ... The minimal dimensions of the access control and the ... installations offer considerable freedom of design with regard to ...
(Date:4/14/2016)... , April 14, 2016 ... Malware Detection, today announced the appointment of Eyal ... new role. Goldwerger,s leadership appointment comes at ... heels of the deployment of its platform at several ... biometric technology, which discerns unique cognitive and physiological factors, ...
(Date:3/31/2016)... R.I. , March 31, 2016  Genomics firm ... of founding CEO, Barrett Bready , M.D., who ... members of the original technical leadership team, including Chief ... President of Product Development, Steve Nurnberg and Vice President ... returned to the company. Dr. Bready served ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... ... June 27, 2016 , ... Cancer experts ... they believe could be a new and helpful biomarker for malignant pleural mesothelioma. ... here to read it now. , Biomarkers are components in the blood, ...
(Date:6/27/2016)... Ginkgo Bioworks , a leading organism design company ... as one of the World Economic Forum,s Technology ... companies. Ginkgo Bioworks is engineering biology to manufacture ... the nutrition, health and consumer goods sectors. The ... Fortune 500 companies to design microbes for their ...
(Date:6/23/2016)... ... June 23, 2016 , ... Mosio, a leader ... “Clinical Trials Patient Recruitment and Retention Tips.” Partnering with experienced clinical research professionals, ... providing practical tips, tools, and strategies for clinical researchers. , “The landscape of ...
(Date:6/23/2016)... -- Houston Methodist Willowbrook Hospital has signed a ... serve as their official health care provider. As ... provide sponsorship support, athletic training services, and most ... athletes and families. "We are excited ... to bring Houston Methodist quality services and programs ...
Breaking Biology Technology: