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<DIV class=article-heading><FONT size=3>A blue whale's exposure to various
pollutants has been pinned down using earwax extracted after its
death.</FONT></DIV>
<DIV class=article-heading><FONT size=4>Whale earwax a time capsule for stress
and toxins</FONT></DIV>
<DIV><FONT size=3>Fat-rich plug reveals chemical signatures of flame retardants
and mercury.</FONT></DIV>
<DIV class=popup-parent data-role="popup-parent"><SPAN class=vcard><A class=fn
href="http://www.nature.com/news/whale-earwax-a-time-capsule-for-stress-and-toxins-1.13750?WT.ec_id=NEWS-20130917#auth-1"
data-popup-width="estimate"><FONT size=3>Olive Heffernan</FONT></A></SPAN></DIV>
<DIV class=pubdate-and-corrections><TIME datetime="2013-09-16" pubdate><FONT
size=3>16 September 2013</TIME></FONT></DIV>
<DIV class="cleared article-tools extra"><FONT size=3></FONT> </DIV>
<DIV class=section>
<DIV class="content no-heading cleared main-content">
<DIV class="related-stories-box box"><FONT size=3>Wax inside a whale’s ear
stores all sorts of useful information on the animal’s exposure to pollutants
and stress levels throughout life, researchers have found.</FONT></DIV>
<P><FONT size=3>The team, led by Sascha Usenko, a environmental scientist at
Baylor University in Waco, Texas, extracted an earplug from a blue whale
(<I>Balaenoptera musculus</I>) killed in a collision with a ship off the coast
of Santa Barbara, California, in 2007 and found it had come into contact with
several organic pollutants and contained high levels of the stress hormone
cortisol as it reached sexual maturity.</FONT></P>
<P><FONT size=3>“It’s difficult to recover time-specific information on chemical
exposure for almost any animal,” says Stephen Trumble, a biologist also at
Baylor and a co-author of the study, published in <I>Proceedings of the National
Academy of Sciences </I>this week<SUP><A id=ref-link-1 class=ref-link
title="Trumble, S. J., Robinson, E. M., Berman-Kowalewski, M., Potter, C. W. & Usenko, S. Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1311418110 (2013)."
href="http://www.nature.com/news/whale-earwax-a-time-capsule-for-stress-and-toxins-1.13750?WT.ec_id=NEWS-20130917#b1">1</A></SUP>.
That is especially true of the relatively rare blue whale, the world’s largest
inhabitant.</FONT></P>
<P><FONT size=3>Decimated by historic whaling practices, blue whales number just
5,000–12,000 individuals worldwide, and they are threatened by entanglement in
fishing nets, environmental noise and pollution. Scientists have long used whale
blubber as a record of the chemicals that these enormous creatures absorb as
they traverse the ocean. But analysis of blubber does not indicate when chemical
contamination occurred, or how long it lasted.</FONT></P>
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<DIV
style="PADDING-BOTTOM: 1px; PADDING-LEFT: 1px; PADDING-RIGHT: 1px; PADDING-TOP: 1px"
class=img-content><FONT size=3><IMG alt=""
src="http://www.nature.com/polopoly_fs/7.12496.1379348487!/image/earplug%20copy.jpg_gen/derivatives/landscape_400/earplug%20copy.jpg">
</FONT>
<P class=caption><FONT size=3>The extracted whale ear plug was 25.4 centimetres
long.</FONT></P></DIV></DIV>
<P><FONT size=3>Whale earwax is a fat-rich deposit that stores the same chemical
data as blubber. But it also records time — similarly to the rings of a tree,
the wax is laid down in light and dark bands, with each band correlating roughly
to a six-month period. In baleen, or filter-feeding, whales, earwax forms a
solid plug that may be tens of centimetres long and remains intact even after
its death.</FONT></P>
<H2><B><FONT size=3>Chemical signatures</FONT></B></H2>
<P><FONT size=3>Usenko and his team identified their specimen as a male aged
about 12 years. During his brief life he came into contact with 16 persistent
organic pollutants, including pesticides and flame retardants. Exposure to the
most persistent chemicals was greatest in the first year — and accounted for
one-fifth of his total lifetime contact — suggesting a transfer of contaminants
from his mother in the womb and during nursing.</FONT></P>
<P><FONT size=3>Maternal transfer of pollutants is known to happen in other
mammals, such as seals and humans. <SPAN>Once these compounds</SPAN><SPAN> enter
the food chain, they are passed on and accumulate.</SPAN> “Some of these
chemicals are no longer in use, such as flame retardants that were outlawed in
2005, but they can stick around for 50 or 60 years,” says Usenko. Other
toxins uncovered from the earwax were probably picked up along the way. Mercury
— which can cause brain damage — spiked twice in the sample, at around five and
ten years.</FONT></P>
<P><FONT size=3>Over the whale’s life, concentrations of cortisol, a stress
hormone, doubled. The peak was directly after the whale reached sexual maturity,
at about ten years old, suggesting stress from sexual competition. But it is
unclear whether the overall increase was caused by natural events, such as
weaning, or by human activities, such as pollution and noise.</FONT></P>
<P><FONT size=3>The research is “exciting”, says Jeremy Goldbogen, a marine
biologist at Cascadia Research Collective in Olympia, Washington, but “the
inability to distinguish baseline stress levels from those associated with
anthropogenic disturbances is a limitation of the study.”</FONT></P>
<P><FONT size=3>Usenko and his team are now hoping to investigate that question
by analysing some of the 1,000 or more whale specimens in museums worldwide. “If
we can look at individuals that lived in an environment without some of the
stresses we see now, then we could tease out the causes of the cortisol
increase,” he says.</FONT></P></DIV>
<DL class=citation>
<DT><A href="javascript:;" jQuery164082182747953835="8"><FONT color=#000000
size=3><STRONG>References</STRONG></FONT></A></DT></DL></DIV>
<DIV id=references class="section expanded">
<DIV class=content>
<OL class=references>
<LI id=b1>
<P><FONT size=3><SPAN class="vcard author"><SPAN class=fn>Trumble, S.
J.</SPAN></SPAN>, <SPAN class="vcard author"><SPAN class=fn>Robinson, E.
M.</SPAN></SPAN>, <SPAN class="vcard author"><SPAN class=fn>Berman-Kowalewski,
M.</SPAN></SPAN>, <SPAN class="vcard author"><SPAN class=fn>Potter, C.
W.</SPAN></SPAN> & <SPAN class="vcard author"><SPAN class=fn>Usenko,
S.</SPAN></SPAN> <SPAN class=source-title>Proc. Natl Acad. Sci. USA</SPAN>
</FONT><A href="http://dx.doi.org/10.1073/pnas.1311418110"><FONT
size=3>http://dx.doi.org/10.1073/pnas.1311418110</FONT></A><FONT size=3>
(<SPAN class=year>2013</SPAN>). </FONT><A class="context-link show"
href="javascript:;"><FONT size=3>Show
context</FONT></A></P></LI></OL></DIV></DIV></FONT></BODY></HTML>