Possibility of hypoxic oceans

Has any scientist suggested that increased CO-2 could result in a drop in oxygen levels in the ocean severe enough to cause a mass-extinction event?

that nature would react to increased CO2 with increased plant growth.

But then again, I'm not a life-sciences person.

I left out an intermediary step: warming. Warm ocean waters can't hold as much oxygen as colder waters. Another thing: the CO-2 in the ocean changes the pH level...more acidic I think. And that affects marine life, too.

I'm certainly no expert but found the following:

At least one journal paper suggests that there is an increase in animal marine animal mortality with increased CO2 levels.

http://www.agu.org/pubs/crossref/2005/2004JC002561.shtml

And some evidence that there is a correlation between higher atmospheric CO2 and mass extinctions in history.

http://ioc.unesco.org/IOCCP/HighCO2/Sequestration/Poertner-OSPAR-Workshop%5B1%5D.ppt

May I suggest googling "ocean hypoxia CO2".

Happy investigations.

Currently, CO₂ is not the primary cause:

http://oceanservice.noaa.gov/products/pubs_hypox.html
http://www.cop.noaa.gov/stressors/pollution/current/gomex-factsheet.html
http://www.sciencedaily.com/releases/2004/08/040810091946.htm
http://www.sciencedaily.com/releases/2006/04/060402220803.htm

and check out
"Under a Green sky"
by Peter Ward


University of Washington paleontologist Peter D. Ward demonstrates in UNDER A GREEN SKY that the ancient past is not just of academic concern. Everyone has heard about how an asteroid did in the dinosaurs, and NASA and other agencies now spend large sums of money tracking so–called near Earth objects. Unfortunately, we may not be protecting ourselves against the likeliest cause of our species' demise. Ward's argument, which has been presented to his peers via several papers in Science, is that all but one of the major extinction events in the history of the world have been brought on by climate change–the same global warming that we are experiencing today.


also
http://www.york.ac.uk/admin/presspr/pressreleases/massextinctions.htm

Global temperatures predicted for the coming centuries may trigger a new ‘mass extinction event’, where over 50 per cent of animal and plant species would be wiped out, warn scientists at the Universities of York and Leeds.

The research team has, for the first time, discovered a close association between Earth climate and extinctions in a study that has examined the relationship over the past 520 million years — almost the entire fossil record available.

"Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner"
Dr Peter MayhewMatching data sets of marine and terrestrial diversity against temperature estimates, evidence shows that global biodiversity is relatively low during warm ‘greenhouse’ phases and extinctions relatively high, while the reverse is true in cooler ‘icehouse’ phases.


http://www.rochester.edu/news/show.php?id=1395