Ocean warming to cancel increased CO2-driven productivity

April 27, 2017
Credit: CC0 Public Domain

University of Adelaide researchers have constructed a marine food web to show how climate change could affect our future fish supplies and marine biodiversity.

Published today in Global Change Biology, the researchers found that high CO2 expected by the end of the century which causes will boost production at different levels of the web, but warming cancelled this benefit by causing stress to marine animals, preventing them using the increased resources efficiently for their own growth and development. The result was a collapsing food web.

"Humans rely heavily on a diversity of services that are provided by ocean ecosystems, including the food we eat and industries that arise from that," says project leader Professor Ivan Nagelkerken, from the University's Environment Institute.

"Our understanding of what's likely to happen has been hampered by an over-reliance on simplified laboratory systems centred on single levels of the food web. In this study, we created a series of three-level food webs and monitored and measured the results over a number of months to provide an understanding of future food webs under climate change."

The researchers constructed marine food webs based on plants which use sunlight and nutrients to grow (algae), small invertebrates that graze on the plants (such as shrimp), and that in turn prey on small invertebrates. They had 12 large aquaria with different species to mimic seagrass, open sand and rocky reef habitats, simulating tidal movements with circular currents.

The food webs were exposed to the levels of ocean acidification and warming predicted for the end of this century. Over several months, the researchers assessed the basic processes that operate in food webs like predation and growth of organisms.

"Elevated boosted plant growth; more plant food meant more small invertebrates, and more small invertebrates, in turn, allowed the fish to grow faster," says PhD candidate Silvan Goldenberg, who is supervised by Professor Nagelkerken and Professor Sean Connell.

"However, ocean warming cancelled this benefit of elevated carbon dioxide by causing stress to the animals, making them less efficient feeders and preventing the extra energy produced by the plants from travelling through the food web to the fish. At the same time, fish were getting hungrier at higher temperatures and started to decimate their prey, the small invertebrates."

The researchers found that ocean warming would be an overwhelming stressor that made food webs less efficient, neutralised the 'fertilising' effect of elevated carbon dioxide and threw the fragile relationship between predators and prey off balance.

"The consequences for marine ecosystems are likely to be severe," says Professor Nagelkerken. "Oceans in the future may provide less fish and shellfish for us to eat, and larger animals that are at the top of the food web, in particular, will suffer. We hope this study will provide predictive understanding which is critical for effective fisheries management."

Explore further: Sharks' hunting ability destroyed under climate change

More information: Global Change Biology (2017). DOI: 10.1111/gcb.13699

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humy
4.3 / 5 (6) Apr 27, 2017
I am impressed that they didn't just stick to computer simulations and did actual reproducible PHYSICAL simulations; that makes their science pretty solid and impossible for any rational person to just simply dismiss their results and conclusions without at least explaining some kind of very good reason for such a dismissal.
I would think it must be hard to ague against their experimental results.
somefingguy
4 / 5 (4) Apr 27, 2017
I am impressed that they didn't just stick to computer simulations and did actual reproducible PHYSICAL simulations; that makes their science pretty solid and impossible for any rational person to just simply dismiss their results and conclusions without at least explaining some kind of very good reason for such a dismissal.
I would think it must be hard to ague against their experimental results.


The issue here is that the sort of people who refute global warming, or any other science that doesn't align with their flawed view of the world, do not care about evidence; whether experimental or simulated on a computer.
antialias_physorg
4.4 / 5 (7) Apr 27, 2017
The issue here is that the sort of people who refute global warming, or any other science that doesn't align with their flawed view of the world, do not care about evidence; whether experimental or simulated on a computer.

Well, there's no end of posts on here where people proclaim "CO2 is plant food therefore more CO2 is good."

What do you say to someone whose ideas are that simplistic (and who even thinks that such statements are smart)? There's really no point in arguing because any kind of argument centered on real facts is beyond them.
Dug
not rated yet Apr 27, 2017
What the short term consideration doesn't consider is longer term adaptations. There will be collapses, but there will be eventual adaptations. This is still no excuse for the gross human overpopulation of the planet.
humy
5 / 5 (1) Apr 28, 2017
This is still no excuse for the gross human overpopulation of the planet.

actually, the real problem isn't human overpopulation but rather bad politics encouraging wasteful polluting unsustainable use of the limited resources. If you look at the statistics, the global human birth rate is currently leveling off i.e. no longer increasing significantly and, besides, the next world war will take cure of any overpopulation that might exist just fine so, no need to loose sleep over overpopulation.
zinger
not rated yet Apr 28, 2017
I've been thinking about ordering a CO2 generator for my green house to see if it would be worth the investment and all the anti Trump hyperbole from this site and others has went a long way in me deciding to go ahead with it. As money will allow I would like to have them installed in my entire greenhouse, it isn't very big compared to some but I have over sixty acres and I could expand plenty especially if I can get the frames cheaply second hand like I did this one. I've also been wanting to start growing fodder in one and get some Highland cattle for a hobby/small farming operation. With the added benefit of doing my part for the environment.
Forestgnome
3 / 5 (2) Apr 29, 2017
I am impressed that they didn't just stick to computer simulations and did actual reproducible PHYSICAL simulations; that makes their science pretty solid and impossible for any rational person to just simply dismiss their results and conclusions without at least explaining some kind of very good reason for such a dismissal.
I would think it must be hard to ague against their experimental results.


It is quite easy to argue with the results. While I agree it's great to see an actual experiment, it fails to account for the vastness of the ocean environment. Just like on land, when the environment becomes unsuitable for a species, it migrates. Experimentally recreating this is nearly impossible, but I'm sure their data is useful in some way or another. It just can't be used to conclude ocean life will die off if their warming scenario occurs.
humy
3 / 5 (4) Apr 30, 2017


It is quite easy to argue with the results. While I agree it's great to see an actual experiment, it fails to account for the vastness of the ocean environment. Just like on land, when the environment becomes unsuitable for a species, it migrates.

Forestgnome

How can some marine organisms migrating away from where the ocean has become too hostile for much of life prevent the disaster of much of the ocean becoming hostile for much of life? You make no sense.
+ acidification will occur everywhere in the ocean so, for those species specifically badly effected by it, there will be nowhere to migrate to to escape it.
So it isn't "quite easy" to argue with their results; it is hard.
Da Schneib
5 / 5 (2) Apr 30, 2017
Not to put too fine a point on it, but it appears that extra productivity due to CO2 enhancement is a myth in 50% of our oxygen production system and questionable in the other 50% due to various climate effects like drought, decreased nitrogen fertilization, and other effects the AGW deniers commonly ignore.

The deniers lied again.

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