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<DIV class=article-heading><FONT size=4>Floating tubes test sea-life
sensitivity</FONT></DIV></HGROUP>
<DIV>Ocean labs probe effects of ocean acidification on ecosystems.</DIV>
<DIV><SPAN class=vcard><A class=fn
href="http://www.nature.com/news/floating-tubes-test-sea-life-sensitivity-1.13271?WT.ec_id=NATURE-20130627#auth-1">Hristio
Boytchev</A></SPAN></DIV>
<DIV class=pubdate-and-corrections><TIME datetime="2013-06-26" pubdate>NATURE,
26 June 2013</DIV>
<DIV class=pubdate-and-corrections><A
href="http://www.nature.com/news/floating-tubes-test-sea-life-sensitivity-1.13271?WT.ec_id=NATURE-20130627">http://www.nature.com/news/floating-tubes-test-sea-life-sensitivity-1.13271?WT.ec_id=NATURE-20130627</A></DIV>
<DIV class=pubdate-and-corrections></TIME></DIV></HEADER><SECTION>
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<DIV style="MAX-WIDTH: 632px" class=caption align=center><FONT
size=1>Researchers suspend 20-metre-tall sacs in a Swedish fjord to enclose
entire ecosystems for study.</FONT></DIV>
<DIV class=credit align=center><FONT size=1>Maike Nicolai/GEOMAR</FONT></DIV>
<DIV class=credit align=center><FONT size=1></FONT> </DIV>
<DIV class=article-tools>Global warming is not the only worrying consequence of
rising carbon emissions. As levels of carbon dioxide increase in the atmosphere,
more of the gas dissolves into the oceans, making the water more acidic. Marine
scientists fear that the conditions will disrupt ecosystems by, for example,
inhibiting some organisms’ ability to build shells. Yet the effects are unclear:
in small-scale laboratory tests, certain species have proved surprisingly
resilient, and some even flourish.</DIV>
<P class="content no-heading cleared main-content">Marine biologist Ulf
Riebesell says that these results tell only part of the story: scientists need
to scale up and examine whole ecosystems. Lab studies of isolated species ignore
variables such as competition, predation and disease, he says. Even minor
effects of acidification on the fitness of individual species — especially small
photosynthetic organisms such as phytoplankton — can upset food chains,
eventually harming larger species. “If you only focus on the lab results, you
are being misled,” he says.<A name=lab></A></P>
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src="http://www.nature.com/polopoly_fs/7.11231.1372180275!/image/mesocoms.jpg_gen/derivatives/landscape_400/mesocoms.jpg"
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<DIV class=lightbox-icon><A class="lightbox-link hide-text" title=Expand
href="javascript:;">Expand</A></DIV>
<P style="PADDING-RIGHT: 25px" class=credit>JASIEK krzysztofiak/nature; Source:
Ref. 2</P></DIV></DIV>
<P class="content no-heading cleared main-content">Riebesell and his colleagues
at GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, have developed
innovative experimental environments — 20-metre-tall sacs suspended in the
ocean, which enclose entire ecosystems and allow the effects of elevated
CO<SUB>2</SUB> to be measured. The first results, published this year, suggest
that some plankton thrive in acidic environments and can wreak havoc on food
chains<SUP><A id=ref-link-1 class=ref-link
title="Brussaard, C. P. D. et al. Biogeosciences 10, 719–731 (2013)."
href="http://www.nature.com/news/floating-tubes-test-sea-life-sensitivity-1.13271?WT.ec_id=NATURE-20130627#b1">1</A></SUP>.
Another experiment will end in July, and preliminary evidence suggests that
conches and sea urchins are vulnerable to acidification.</P>
<P class="content no-heading cleared main-content">The project is inspired by
analogues on land, in which swathes of forest are bathed in extra CO<SUB>2</SUB>
to study the effects on plant life (see <A
href="http://www.nature.com/uidfinder/10.1038/496405a"><I>Nature </I><B>496,</B>
405–406; 2013</A>). For the sea, Riebesell and his colleagues constructed
‘mesocosms’ — floating cylinders of thin plastic that function like giant
test tubes<SUP><A id=ref-link-2 class=ref-link
title="Riebesell, U. et al. Biogeosciences 10, 1835–1847 (2013)."
href="http://www.nature.com/news/floating-tubes-test-sea-life-sensitivity-1.13271?WT.ec_id=NATURE-20130627#b2">2</A></SUP>.
When first put into the water, the sacs are left open at the top and bottom,
allowing hundreds of small species to enter. After several days, they are closed
and acidified water is pumped in (see <A
href="http://www.nature.com/news/floating-tubes-test-sea-life-sensitivity-1.13271?WT.ec_id=NATURE-20130627#lab">‘Sea
lab’</A>). Over weeks or months, researchers measure how the ecosystems inside
fare in comparison with those in untreated sacs.</P>
<P class="content no-heading cleared main-content">Realizing this simple idea
has been challenging. The scientists began in 2006 with a prototype,
free-floating in the Baltic Sea, that floated too well: currents carried it
along much faster than expected, and the scientists had to chase it in a
research ship. After only two days they reached Swedish waters, for which they
had no research permits. When they tried to recover the mesocosm, it
broke.</P>
<P class="content no-heading cleared main-content">The team conducted its first
successful experiment in 2010, using a lighter design that was moored in place
in the Norwegian Arctic archipelago of Svalbard. The researchers found that,
compared with the controls, the acidic mesocosms produced less dimethyl
sulphide<SUP><A id=ref-link-3 class=ref-link
title="Archer, S. D. et al. Biogeosciences 10, 1893–1908 (2013)."
href="http://www.nature.com/news/floating-tubes-test-sea-life-sensitivity-1.13271?WT.ec_id=NATURE-20130627#b3">3</A></SUP>
— a gas that helps to form clouds, which reflect sunlight and can counteract
climate warming. Riebesell is not sure what causes the change; he thinks that
the plankton in the mesocosm might be making less of the gas, or the acidic
water could be affecting its stability.</P>
<P class="content no-heading cleared main-content">Picophytoplankton, the
smallest photosynthetic organisms, turned out to grow better in the acidic
mesocosms<SUP><A id=ref-link-4 class=ref-link
title="Brussaard, C. P. D. et al. Biogeosciences 10, 719–731 (2013)."
href="http://www.nature.com/news/floating-tubes-test-sea-life-sensitivity-1.13271?WT.ec_id=NATURE-20130627#b1">1</A></SUP>.
But at the same time, diatoms — larger algae that are among the most important
producers of ocean biomass — suffered. The change could mean that more nutrients
are cycled among the picophytoplankton rather than reaching larger animals
such as fish. Indeed, preliminary results from the latest experimental run
indicate that larvae of sea urchins and Strombidae conches are barely surviving
in the acidic mesocosms. However, the scientists think that food quality may not
be the main reason for their demise; pathogens and problems making shells could
also have a role.</P>
<DIV class="related-stories-box box">Adina Paytan, an oceanographer at the
University of California, Santa Cruz, says that Riebesell’s work “fills an
important niche between lab work and field studies” and has “advanced the field
considerably”. She takes a different systems approach to acidification, studying
‘natural mesocosms’: underwater springs off Mexico that enrich zones in
CO<SUB>2</SUB>.</DIV>
<P class="content no-heading cleared main-content">Riebesell says that these
regionsare a good lab for studying immobile seagrasses, but not organisms that
can move freely. Paytan notes that there are problems with Riebesell’s
mesocosms: for example, the plastic walls filter out some ultraviolet light,
removing a natural stressor for photosynthetic organisms. And the tubes are
impermeable, so nutrients in the water become exhausted, and experiments last
only a few months. Nevertheless, Paytan says, “we still learn a great lot from
these experiments”.</P>
<P class="content no-heading cleared main-content">This year’s run, in the
Swedish Gullmar Fjord, uses five control mesocosms and five in which acidity is
boosted to levels associated with the atmospheric CO<SUB>2</SUB> concentrations
predicted for the year 2100. The experiment will end next month after a 6-month
run — the longest yet — during which the researchers have monitored a natural
plankton bloom.</P>
<P class="content no-heading cleared main-content">Riebesell and his team seem
comfortable with using their mesocosms as a hybrid between a controlled
laboratory environment and a natural one. They have introduced fish eggs into
the ecosystems for the first time, and Matias Scheinin, a marine biologist at
GEOMAR, is using the sacs to explore natural selection. By tracking the
abundance of individual strains of diatoms — which can undergo hundreds of
generations in a few months — he hopes to identify those that flourish in acidic
environments. He will screen them for the genes responsible, to investigate
rates and mechanisms of adaptation.</P>
<P class="content no-heading cleared main-content">Oceans have gone through
major acidification events during climate change in the ancient past. By
accelerating evolution, Scheinin wants to get a glimpse of their future. “I have
some hope that evolution can help marine life deal with acidification,” he says.
“It’s not the first time it has had to go through it.”</P>
<DIV class=section>
<DL class=citation>
<DT>See Comment <A href="http://www.nature.com/uidfinder/10.1038/498429a">page
429</A></DT></DL></DIV></SECTION><SECTION>
<DIV class="section-heading toggle"><A href="javascript:;"
jQuery164015485991319152653="8"><STRONG><FONT
color=#000000>References</FONT></STRONG></A></DIV>
<DIV class="section expanded">
<DIV class=content>
<OL class=references>
<LI id=b1>
<P><SPAN class="vcard author"><SPAN class=fn>Brussaard, C. P. D.</SPAN></SPAN>
<I>et al</I>. <SPAN class=source-title>Biogeosciences</SPAN> <SPAN
class=volume>10</SPAN>, <SPAN class=start-page>719</SPAN>–<SPAN
class=end-page>731</SPAN> (<SPAN class=year>2013</SPAN>). <A
href="http://dx.doi.org/10.5194/bg-10-719-2013">Article</A> <A
href="http://links.isiglobalnet2.com/gateway/Gateway.cgi?amp;GWVerhttp://links.isiglobalnet2.com/gateway/Gateway.cgi?amp;GWVersion=2&SrcAuth=Nature&SrcApp=Nature&DestLinkType=FullRecord&KeyUT=000315093000006&DestApp=WOS_CPL">ISI</A> <A
class="context-link show" href="javascript:;">Show context</A></P></LI>
<LI id=b2>
<P><SPAN class="vcard author"><SPAN class=fn>Riebesell, U.</SPAN></SPAN> <I>et
al</I>. <SPAN class=source-title>Biogeosciences</SPAN> <SPAN
class=volume>10</SPAN>, <SPAN class=start-page>1835</SPAN>–<SPAN
class=end-page>1847</SPAN> (<SPAN class=year>2013</SPAN>). <A
href="http://dx.doi.org/10.5194/bg-10-1835-2013">Article</A> <A
href="http://links.isiglobalnet2.com/gateway/Gateway.cgi?amp;GWVerhttp://links.isiglobalnet2.com/gateway/Gateway.cgi?amp;GWVersion=2&SrcAuth=Nature&SrcApp=Nature&DestLinkType=FullRecord&KeyUT=000317010600039&DestApp=WOS_CPL">ISI</A> <A
class="context-link show" href="javascript:;">Show context</A></P></LI>
<LI id=b3>
<P><SPAN class="vcard author"><SPAN class=fn>Archer, S. D.</SPAN></SPAN>
et al. <SPAN class=source-title>Biogeosciences</SPAN> <SPAN
class=volume>10</SPAN>, <SPAN class=start-page>1893</SPAN>–<SPAN
class=end-page>1908</SPAN> (<SPAN class=year>2013</SPAN>). <A
href="http://dx.doi.org/10.5194/bg-10-1893-2013">Article</A> <A
href="http://links.isiglobalnet2.com/gateway/Gateway.cgi?amp;GWVerhttp://links.isiglobalnet2.com/gateway/Gateway.cgi?amp;GWVersion=2&SrcAuth=Nature&SrcApp=Nature&DestLinkType=FullRecord&KeyUT=000317010600043&DestApp=WOS_CPL">ISI</A> <A
class="context-link show" href="javascript:;">Show
context</A></P></LI></OL></DIV></DIV></FONT></BODY></HTML>