Scientists sound acid alarm for plankton

May 15, 2012 By Tom Marshall
Scientists sound acid alarm for plankton
Coloured scanning electron micrograph (SEM) of Emiliania huxleyi.

The microscopic organisms on which almost all life in the oceans depends could be even more vulnerable to increasingly acidic waters than scientists realised, according to a new study.

Previous experiments have given an unduly optimistic view of the impact of acidifying oceans on ; it turns out that the methods used may have biased their results.

"Plankton often grow in or aggregates," says Professor Kevin Flynn of Swansea University, lead author of the study. "But the way they are handled tends to break these clumps up. When a scientists starts working on a plankton sample in the lab, the first thing they do is give it a good shake."

How acidity affects depends greatly on the size of the aggregate they're in, so studying plankton whose intricate communities have been disrupted doesn't give an accurate picture of the conditions they will face in the wild.

To correct this distortion, UK and Australian researchers used to examine the immediately around the bodies of plankton in varying conditions. They found that if predictions of general come true, many kinds of plankton will face much more , and more widely varying conditions over each day, than previously realized – conditions far beyond anything seen in recent history. The results are likely to be stunted growth, or even death.

Ocean acidification (OA) is happening as the carbon dioxide we release into the atmosphere dissolves in seawater to form a weak acid. Scientists predict that by the end of the century, the oceans' average pH level will drop by 0.3 units - the lower the value, the more acidic. This doesn't sound like a big change, but it equates to a doubling in acidity. Many organisms may struggle to deal with such changes, particularly those that grow external skeletons out of calcium carbonate, which can dissolve in acid conditions.

Everything from crustaceans and corals to microscopic algae could be at risk; this study focused on the key drivers of the planktonic community. These are among the most important living things on Earth; they form the base of the ocean food pyramid, turning sunlight into nourishment for grazing animals and ultimately predators.

The photosynthetic algae absorb CO2 through photosynthesis; when they die, their bodies sink to the seabed where much of the carbon they absorbed in life is stored for long periods. Some of this material now exists as chalk; much of it was converted to oil and gas which we now extract and burn. This means these organisms form a vital part of the global carbon cycle.

Flynn explains that understanding the effects of OA on particular living things is much more complex than it might seem. Even apart from the effects of their tendency to group together, the metabolic processes of very small marine organisms can have a serious effect on the conditions close to them. This means these organisms don't simply face the conditions found in seawater at a large scale; they create their own microenvironment.

"Different types of plankton will experience different conditions depending on their sizes and metabolic rates," Flynn says. Living things that are photosynthesising absorb carbon dioxide from the water around them, making it less acidic; conversely those that are respiring absorb oxygen and emit CO2, increasing the ambient acidity.

The results suggest that ocean acidification could change the mix of plankton living in the oceans, with species that can't deal with changed conditions losing out to those that can. Calcifying plankton are likely to be among the hardest-hit, because the chemical processes involved in forming their chalky shells themselves contribute to making their immediate surroundings more acidic. In another twist, as seawater gets more acidic, its capacity to protect against even more acidity diminishes, so general ocean acidification will increase the impact of the local acidification that plankton trigger.

But Flynn says OA's impact will be complex. While calcifying plankton are alive, it's possible they may be able to stave off too much damage to their shells; a more important consideration for the wider environment is what happens after they die. If their skeletons dissolve instead of sinking to the seabed and being locked up in sediments, then there are important implications for the carbon cycle. But all this assumes that conditions under OA allow them to grow in the first place, and this research indicates the difference in the acid micro-climate that calcifiers and non-calcifiers will endure.

The researchers now plan to turn their attention to other marine animals that may be at risk, including the early stages of fish and shellfish - these are microscopically tiny, forming part of the plankton, so are subject to similar small-scale environmental effects. Flynn is also leading a NERC-funded project in collaboration with the Department for the Environment, Food and Rural Affairs to investigate OA's impact on commercial fisheries.

The Natural Environment Research Council (NERC) provided the primary funding for the study, which appears in Nature Climate Change. Its authors included scientists from Plymouth Marine Laboratory, the Marine Biological Association and the universities of Swansea and Dundee in the UK, and from the University of Technology Sydney and Monash University, Victoria in Australia.

Explore further: Romanian city opens plastic bottle bridge in litter protest

More information: Changes in pH at the exterior surface of plankton with ocean acidification, Kevin J. Flynn, et al. Nature Climate Change (2012) doi:10.1038/nclimate1489

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User comments : 7

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Sean_W
2.6 / 5 (10) May 15, 2012
"To correct this distortion, UK and Australian researchers used computer simulations" blah blah blah.


This would be funny if it were not so pathetic. These are not simulations they are theatre.
DavidHumus
3 / 5 (8) May 15, 2012
And you know this because...? Oh wait, you're a climate-change denier on the wrong page. Here, let me help you out, I'll type this very s..l..o..w..l..y: this article is about acidification of the oceans because of increasing CO2 levels.
Terriva
1.8 / 5 (5) May 15, 2012
There is still one big IF. From historical record it seems, the elevated concentration of carbon dioxide preceded the period of global warming by about one hundred years. The oceans contain about 50 times more CO2 than the atmosphere and 20 times more than the land biosphere. Just the mild warming of deep sea marine water will release a huge amount of carbon dioxide into atmosphere. The heating of bottom of ocean and permafrost soil may release a huge portion of methane into atmosphere too, which will increase the carbon dioxide concentration in the marine water subsequently. The methane itself is significant greenhouse gas and the decomposition of its clathrates will accelerate the global warming in avalanche-like way.

The massive burning of fossil fuels undoubtedly contributes to the acidification of the oceans - but the open question still is, how this contribution actually is significant.
nuge
5 / 5 (2) May 16, 2012
Could anyone explain the mechanism for this result? I don't quite understand...I'd have thought that if the organisms are clumped, it would decrease their overall surface area, and hence reduce the reaction with the acid.
StarGazer2011
2.3 / 5 (3) May 16, 2012
Could anyone explain the mechanism for this result? I don't quite understand...I'd have thought that if the organisms are clumped, it would decrease their overall surface area, and hence reduce the reaction with the acid.


The model took care of that; they began with their desired (and grant generating) result set and worked backwards same as always with CAGW.
stealthc
1 / 5 (1) May 16, 2012
lol excellent feedback these green fascists are definitely at it again. Seems like they do this a few times every day with their so-called discoveries such as this bogus sounding work. These scientists will stop at nothing until we are THEIR sheep, only problem is they are being used by thieving bankers, who in turn are being used by elite families to try and socially engineer us into their world government. This is no joke, you'll see another year of the system's crap and there won't be anyone left doubting it.
Birger
5 / 5 (3) May 16, 2012
There are two ways you can find out what is happening:
You can wait until it is too late to do anything, in which case you get a 100% correct description by observing what just happened.
Or you can try to predict what will happen... you know, with computers and stuff... when plankton travel through areas with different acidity every day.
This is worth finding out because "they form the base of the ocean food pyramid".

I see a pattern in the comments. In the sixties people said "we do not need to restrict the anchovy fishery" and the anchovy fish collapsed. In the eighties people said "we do not need to restrict fishing at the Grand Banks" and it collapsed.
Russia: "we do not need to restrict fishing in the Baltic" and now Baltic herring is near collapse.

And now the base of the ocean food pyramid is in trouble. Time for deniers to show up. Have you considered learning from history instead of Fox news? Or would you feel threatened?