Ocean acidification weighing heavily upon marine algae

September 8, 2015, University of Plymouth
Acetabularia acetabulum taken in low CO2 conditions. Credit: Jason Hall-Spencer

Ocean acidification can weaken algal skeletons, reducing their performance and impacting upon marine biodiversity, say scientists in a new research paper published this week.

Even a small loss of skeletal caused by exposure to corrosive waters can have a significant impact and leave algae at risk of losing access to light and nutrients.

Scientists at Plymouth University, the University of Washington, and the University of Palermo, made the discovery during fieldwork at in the Mediterranean and subsequent laboratory testing. Their paper, Ocean acidification bends the Mermaid's wineglass, is the cover story of the new edition of the Royal Society's Biology Letters.

One of the authors, Professor Jason Hall-Spencer, from Plymouth's School of Marine Science and Engineering, and its Marine Institute, said: "Based upon current forecasts, many calcified organisms will be corroded by acidified waters by the end of the century. What this study shows is that a dramatic weakening of algal skeletal strength can have implications for performance, which in turn could transform an entire ecosystem."

The team of scientists conducted the research off the Sicilian island of Vulcano, last year, as part of the EU-funded MedSeA project. Three sites of high, medium and low CO2 were surveyed by snorkel for evidence of the presence and appearance of the green algae Acetabularia acetabulum, also known as 'mermaid's wineglass'.

All surveys revealed that the algae ranged in appearance from those with bright white cups at the low CO2 site to green cups at the high site, and no calcified algae were present in the region nearest the volcanic seeps. When specimens were scanned under electron microscope, they found that those from areas of low CO2 had an intact sheath of aragonite that supported the stem, while those in had had theirs eroded and pitted and were up to 32% less calcified.

Further tests were conducted on samples using static cantilever beam theory, with the base of the algae clamped between two horizontal glass slides, suspending the hydrated stem and cup in air. A weight was then hung from the stem to exert force and test its flexural stiffness and ability to resist the load.

It revealed that the stems from those specimens collected from the high CO2 site were up to 40% less stiff and 40% droopier - raising important questions about the impact upon their performance as a result. And the scientists say the relationship between calcification and material stiffness was exponential, not linear, so even relatively small reductions in calcification led to a disproportionate drop in the ability of the material to resist a load.

"Although calcifying organisms can tolerate high CO2 conditions, even subtle changes in calcification can cause dramatic changes in skeletal performance, which may in turn affect key biotic and abiotic interactions," said Professor Hall Spencer.

Acetabularia acetabulum taken in corrosive water, high in CO2. Credit: Jason Hall-Spencer
"A less rigid stem droops towards the seafloor likely reducing the distance spores can travel away from the cup. The cup is also photosynthetic, so bending may reorient it away from light and increase shading by neighbours, thereby reducing the scope for growth. But there are also potential benefits to being less stiff. A more flexible stem allows the algae to reorient in flow, reducing drag and the likelihood of dislodgement, and may aid in gas exchange as the stem moves back and forth like a pendulum."

Professor Laura Newcomb, of the University of Washington, added: "This study underscores the fact that some organisms may survive ongoing despite reduced calcification; this facultative calcification may explain why certain calcified organisms reappear in the fossil record after mass extinctions associated with periods of high atmospheric CO2.

"Many ocean acidification studies show reduced calcification at high CO2, but do not examine the consequences for organismal performance. Our ecomaterial approach establishes these linkages between calcification and performance (and ultimately fitness) which are vital for long-term predictions of how organisms will fare in a high CO2 world."

Explore further: Rising carbon dioxide levels stunt sea shell growth

More information: Ocean acidification bends the Mermaid's wineglass, Biology Letters, rsbl.royalsocietypublishing.or … .1098/rsbl.2014.1075

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21 comments

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Sanescience
2 / 5 (4) Sep 08, 2015
Meaning less basic, not actually acidic :-P
leetennant
4.2 / 5 (10) Sep 08, 2015
Yes and I'm not getting fatter, I'm actually getting less thin. Yay for me! That's so fundamentally different.
antigoracle
1.7 / 5 (6) Sep 09, 2015
Yes and I'm not getting fatter, I'm actually getting less thin. Yay for me! That's so fundamentally different.

Uh huh and, I could say you are not getting stupider, just less intelligent, but that would require you to be intelligent in the first place. Yayyyy!!

BTW, I'm still waiting for AGW Cult "science" to demonstrate how warming oceans absorb more CO2.
leetennant
4.2 / 5 (10) Sep 09, 2015
Sorry @antigoracle but answering a question 15 times is officially my limit. Maybe others will be more tolerant of your ongoing bullshit.
animah
4.4 / 5 (7) Sep 09, 2015
Sorry @antigoracle but answering a question 15 times is officially my limit


Besides I don't see how this argument benefits antig's position: Given that more CO2 wams oceans more, if warming oceans did not absorb more CO2, that would actually amplify the warming.
Physgirl
1.7 / 5 (6) Sep 09, 2015
The oceans as a whole are highly alkaline, not acidic. The degree of alkalinity varies, but the oceans have always been alkaline, else the fossil record would have a gap in the marine record as carbonate shell of organisms would have dissolved. The ocean is not getting acidified by additional CO2. It is getting neutralized by additional CO2.

Regards
Physgirl
Egleton
1.8 / 5 (5) Sep 09, 2015
Welcome to the fight club physgirl. There are a lot of fragile egos here.
Moebius
4.2 / 5 (5) Sep 09, 2015
Parsing words while the earth burns? We are destroying the ocean and we won't see it until it's too late. For the same reason we don't see it now, familiarity breeds blindness. Freedom breeds Stupidity. Stupidity breeds an economic system based solely on profits at any cost. Profit breeds uncaring for anything else. And freedom renders us unable to change. It's sort of circular, the snake with its tail in its mouth.
antigoracle
1.6 / 5 (7) Sep 09, 2015
Sorry @antigoracle but answering a question 15 times is officially my limit.

Wow, 15 times!
Yet I have to ask again because you are oblivious to the fact that each answer was stupider...er..excuse me..less intelligent, than the one before.
antigoracle
1.6 / 5 (7) Sep 09, 2015
Freedom breeds Stupidity.

Then someone definitely needs to cage you.
thermodynamics
3.9 / 5 (7) Sep 09, 2015
Yes and I'm not getting fatter, I'm actually getting less thin. Yay for me! That's so fundamentally different.

Uh huh and, I could say you are not getting stupider, just less intelligent, but that would require you to be intelligent in the first place. Yayyyy!!

BTW, I'm still waiting for AGW Cult "science" to demonstrate how warming oceans absorb more CO2.


OK Anti: You mentioned this once before and I, sarcastically, asked if you wanted me to show you how to do it and you said yes. So, if you are willing to follow along and ask if you have questions I will take the time to show you how it works. What I explained using a text explanation is that the extra absorption is due to the increase in the partial pressure of CO2 exceeding the increase in temperature (which decreases solubility).

Let me know if you are really serious or if you will just ignore the chemistry.

Also, are you comfortable with calculus or should I stick with arithmetic?
leetennant
4 / 5 (8) Sep 10, 2015
Or you can just refer him here
http://phys.org/n...res.html

or here
http://phys.org/n...ual.html

And of course here

http://www.easych...in-water

where it shows how his question is answered by the basics of chemistry. But then, the build up of energy in the system due to increasing greenhouse gases is pretty basic physics too so it's clear antigoracle isn't interested even in the entry level of the science

And that's ignoring the fact that we know it's happening because... it's happening! We can see it.

http://www.antarc...rn-ocean
http://ocean.si.e...fication
http://www.pmel.n...ation%3F

And no doubt next article he'll "demand" the "answer" again.
moonkoon
1.8 / 5 (5) Sep 14, 2015
I agree with Sanescience, an acid has a pH of less than 7. Any value over 7 is alkaline.

And actually changing the pH of seawater is not so easy. The pH of the ocean is resistant to change as it is a buffered solution. Adding CO2 will simply have the knock-on effect of precipitating more calcium carbonate so that the pH will remain stable.

It is only in places where there are naturally occurring CO2 seeps into seawater that we find localised spots with low pH and even then the water is generally on the alkaline side of 7.
leetennant
3.7 / 5 (6) Sep 14, 2015
Oh good God, whether the ocean is getting LESS basic or MORE acidic doesn't matter. It's the same damn thing. As I said originally, it's like saying you're not getting fatter, you're just getting less thin. In all the stupid, this comes pretty close to the biggest stupid.

I'd say it's like you don't know what the science is actually saying but I think you do; you're just setting up a strawman because it's all you have.
moonkoon
1.8 / 5 (5) Sep 14, 2015
Hi leetennant,

I appreciate your concern for the well-being of the ocean environment but I think your concerns about CO2 induced lowering of the ocean's pH are misplaced.

In my opinion, the bigger threat to pH stability of sea water is the large increase in levels of atmospheric nitrogen oxides that have occurred with the increasing use of internal combustion engines (these same nitrogen oxides are also largely responsible for city smog) and nitrogen fertilizers. And unlike CO2, with nitrogen there is little doubt about its anthropomorphic origin. cont.
moonkoon
1.7 / 5 (6) Sep 14, 2015
And, although the buffering effect still applies, acids of nitrogen have a much lower pH than their carbon cousins so, pound for pound, their 'acidification' effect is much larger. There are of course upsides for this increased nitrogen availability, for as is also the case with CO2, sea flora are potential beneficiaries, ...with consequent knock-on effect on up the food chain. Nitrogen is the basis of protein synthesis and carbon is the basis of cellulose, sugar, starch and oil production by plants.

In terms of relative risk, nitrogen is streets ahead, in my opinion.
thermodynamics
3.9 / 5 (7) Sep 14, 2015
Moonkoon, try this site and see what your disagreement is with it.

http://www.pmel.n...ation%3F

I am curious as to why you think that acidification is incorrect when it is a relative term (not associated with neutral pH).

I am also curious as to whether you understand the log relationship in pH.

The change in pH is substantial and measured. It is not a conjecture or computer generated result.
moonkoon
2 / 5 (4) Sep 15, 2015
Hi thermodynamics,

Yes, people can and do describe the process as acidification. However I feel that many who are not familiar with chemical lingo also take that to mean that sea water now qualifies as an acid, and that is not the case. Like it has been for millions of years, sea water is still alkaline. So my concern here is that the terminology doesn't help people to form a balanced view.

Yes that was covered in one of the classes I took and not only that, it also coincides with the classes where I was paying attention. :-)

In my opinion, the site you mention could be improved by some discussion on buffering, and again I'm not sure talking about percentages in relation to pH variation is helpful in forming an accurate view about the significance of the changes. If percentage is to be used, perhaps it could provide a useful comparison to the 0.1 pH/30% variation by pointing out, say, that a ten point move on the pH scale is about a 900% change in H+ ion concentration.
moonkoon
2 / 5 (4) Sep 15, 2015
And more generally re the measured changes in pH, this is a quote from another NOAA page (being new here, I don't think I am allowed to post links but you can search the quote)

"... Many scientists have observed that natural variability in seawater acidity (and thus pH) is strong and can be much larger on short time scales than the observed and projected changes in acidity due to ocean acidification over the scale of decades to centuries. ..."

So it may be prudent to take the results as provisional, ...again in my opinion.
gkam
2.1 / 5 (7) Sep 15, 2015
moonkoon, instead of all that effluvia, why not just discuss the effects of what is actually happening? We are killing the seas!

Next stop: Soylent Green.
thermodynamics
3.4 / 5 (5) Sep 15, 2015
And more generally re the measured changes in pH, this is a quote from another NOAA page (being new here, I don't think I am allowed to post links but you can search the quote)

"... Many scientists have observed that natural variability in seawater acidity (and thus pH) is strong and can be much larger on short time scales than the observed and projected changes in acidity due to ocean acidification over the scale of decades to centuries. ..."

So it may be prudent to take the results as provisional, ...again in my opinion.


I think they do a great job of explaining it here.

http://pmel.noaa....er+on+pH

Note how they clarify the difference between acidity and alkalinity. This is an important difference. When we see it as acidification they are referring to H+.

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