Rising carbon dioxide levels, ocean acidity may change crucial marine process

Credit: Tiago Fioreze / Wikipedia

Climate change may be putting cyanobacteria that are crucial to the functioning of the ocean at risk as the amount of carbon dioxide in the atmosphere increases and the acidity of ocean water changes.

In a paper published Thursday in Science, a team of researchers from Florida State University, Xiamen University in China and Princeton University argue that the acidification of seawater caused by rising levels makes it difficult for a type of cyanobacteria to perform a process called .

Few people know much about a type of cyanobacteria called Trichodesmium, but this miniscule collection of cells is critical to the health of hundreds of species in the Earth's oceans. Through fixation, Trichodesmium converts nitrogen gas into ammonia and other molecules that organisms are dependent on for survival.

Trichodesmium is thought to be responsible for about 50 percent of marine nitrogen fixation, so a decline in its ability could have a major ripple effect on marine ecosystems.

"This is one of the major sources of nitrogen for other organisms in the open ," said Sven Kranz, assistant professor of Earth, Ocean and Atmospheric Science at Florida State University and a co-author of this study. "If Trichodesmium responds negatively to the environmental changes forced upon the ocean by , it could have a large effect on our food web."

The effects of on Trichodesmium have been studied extensively by scientists in labs across the globe but with widely different results. Some scientists found that increased dioxide in ocean waters caused a decline in nitrogen fixation, while others saw huge increases. Because of the large role these bacteria play in the health of the Earth's oceans, Kranz and his colleagues sought to resolve the discrepancies.

Some of these discrepancies, they found, are based on the preparation of the water in which these organisms typically grow under laboratory conditions. For example, the researchers found contamination by elements such as ammonia or toxic elements like enhanced copper concentration.

"Any slight differences in the specific ingredients of the water—in this case artificial seawater that scientists prepare—can have a huge effect on the outcome," Kranz said.

A slight contamination can throw a huge wrench in the process, yet using this artificial seawater is common because not every lab has access to clean ocean water.

The authors also found that increased carbon dioxide could sometimes stimulate nitrogen fixation but this was offset by the negative effects of the increased ocean acidity.

Kranz began studying how increased carbon dioxide affects cyanobacteria as a researcher in Germany and then as a postdoctoral researcher with François Morel and Dalin Shi at Princeton University. Shi is now at Xiamen University and led the study with his research group there.

For this study, Kranz focused on the preliminary data collections and how the cyanobacteria reacted to changing concentrations of iron and carbon dioxide. Shi's group in China conducted further studies including protein analysis and replicated this work in the field, conducting experiments in the South China Sea in May 2016.

Explore further

More than One: Long-Reigning Microbe Controlling Ocean Nitrogen Shares the Throne

More information: "The complex effects of ocean acidification on the prominent N2-fixing cyanobacterium Trichodesmium," Science (2017). science.sciencemag.org/lookup/ … 1126/science.aal2981
Journal information: Science

Citation: Rising carbon dioxide levels, ocean acidity may change crucial marine process (2017, April 27) retrieved 20 August 2019 from https://phys.org/news/2017-04-carbon-dioxide-ocean-acidity-crucial.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Apr 27, 2017
The key word here is "may" which makes this a scifi idea rather than science. See also AI robots exterminating humanity, genetically modified virus pandemic, black hole from high energy particle collisions and self replicating nano machines consuming the planet. Science is carbon.

Apr 27, 2017
The key word here is "may" which makes this a scifi idea rather than science
the word "may" is used because of the following from the study
The ongoing acidification of seawater caused by anthropogenic CO2 will lead to various direct or indirect effects on marine phytoplankton. Our study reconciles previous results that show opposite effects of acidification on Trichodesmium and demonstrates a significant decrease in N2-fixation by this prominent diazotroph at the seawater pH expected for year 2100, particularly under the Fe-limited conditions that prevail in large oceanic regions. Because Trichodesmium is estimated to contribute up to 50% of marine N2-fixation, acidification could lead to a decline in the supply of new nitrogen to oceanic ecosystems, and this effect would be magnified if other diazotrophs were similarly affected.

Apr 28, 2017
The key word here is "may" which makes this a scifi idea rather than science. .


NO, you simply couldn't be more WRONG; the word 'may' implies probability, and rationally assigned probabilities are at the heart of all valid statistical analyses of scientific data thus is essential for most of good science to be valid. Without any 'may', the only good valid science we would be left with is pure mathematics.

Apr 28, 2017
The link suggests that global warming may reduce certain cyanobacteria performing nitrogen fixation and thus do harm by starving the oceans of fixed nitrogen. But reducing this nitrogen fixation might be a GOOD thing!? -because it may partly offset the excessive and harmful amounts of man made fixed nitrogen pollution entering into the ocean!? -a case of two bad human influences at least partly canceling each other out?
-just a thought.

Apr 28, 2017
All you need to know to understand the illegitimacy of this article is that our planet had 20 times the CO2 during a period of geologic history marked by prolific vegetative growth. More CO2 promotes plant life.

Apr 28, 2017
More CO2 promotes plant life.


NO, that is massively too simplistic. If all else is equal then, at least generally and up to but not beyond a limit, more CO2 promotes plant life; BUT in this case, NOT all is equal so that rule doesn't apply. The beneficial effects on increase in CO2 are likely to be more than offset by the negative effects, such as from the increase frequency of extreme weather events destroying trees, crops, etc.
The illegitimacy of this article is just fine and the past effects of increase in CO2 are rendered irrelevant to that by the fact that other conditions other than CO2 levels were different in the past thus it isn't just CO2 that determined the overall effect; without taking into account those complicating factors, you cannot conclude much from that!

Apr 28, 2017
Homebrook - this article is about marine ecosystems - specifically cyanobacteria - not vegatation. . But as humy points out - there are many other factors to be considered - when drawing conclusions about the climate - and the affect of C02 on our world. There are - Milankovich cycles; atmospheric particulates; ocean levels; plate tectonics; solar activity; weather patterns; glaciation (or lack of); ocean currents; cloud cover; etc. This article is just one tiny piece in a huge jigsaw puzzle.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more