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<DIV class=formatpublished><FONT size=3>Nature</FONT></DIV>
<DIV class=formatpublished>Published online <ABBR class=published
title=2011-09-26T19:00:00Z>26 September 2011</ABBR> </DIV>
<DIV class=formatpublished>doi:10.1038/news.2011.546 </DIV>
<DIV class=type-of-article> </DIV>
<DIV class="heading entry-title"><FONT size=4>Trace amounts of crude oil harm
fish</FONT></DIV>
<DIV class=intro>Deepwater Horizon spill affected gene expression in Gulf
killifish.</DIV>
<DIV class=byline><SPAN class=vcard><SPAN class="author fn">Melissa
Gaskill</SPAN></SPAN></DIV>
<DIV class=byline><SPAN class=vcard><SPAN class="author fn"><A
href="http://www.nature.com/news/2011/110926/full/news.2011.546.html?WT.ec_id=NEWS-20110927">http://www.nature.com/news/2011/110926/full/news.2011.546.html?WT.ec_id=NEWS-20110927</A></SPAN></SPAN></DIV>
<DIV class=byline><SPAN class=vcard><SPAN
class="author fn"></SPAN></SPAN> </DIV><SPAN class=cleardiv><!-- --></SPAN>
<DIV class=entry-content sizset="16" sizcache="4">
<DIV style="WIDTH: 260px" class="inline-image right">
<DIV><IMG alt=marsh
src="http://www.nature.com/news/2011/110926/images/news546-i1.0.jpg"></DIV>
<DIV><SPAN class=imagedescription><FONT size=1>Hydrocarbons from oil spills -
such as those washed up in Barataria Bay, Louisiana - can remain in marsh
sediments for years, potentially having long-term effects on fish embryos.<SPAN
class=imagecredit>Bridget Besaw/Aurora
Photos/Corbis</SPAN></FONT></SPAN></DIV></DIV></DIV>
<P class=entry-content sizset="16" sizcache="4">Heart-breaking pictures of
seabirds covered in black crude oil, arresting as they are, can miss the hidden
story of an oil spill's impact on wildlife.</P>
<P class=entry-content sizset="20" sizcache="1">Exposure to even tiny
concentrations of the chemicals present in oil can also cause harmful biological
effects that usually go unnoticed, according to a study published today in <SPAN
class=i>Proceedings of the National Academy of Sciences</SPAN><SUP sizset="20"
sizcache="1"><A
href="http://www.nature.com/news/2011/110926/full/news.2011.546.html?WT.ec_id=NEWS-20110927#B1">1</A></SUP>.</P>
<P class=entry-content sizset="16" sizcache="4">"It's striking that even though
the analytical chemistry doesn't indicate exposure, the biology does," says
Andrew Whitehead, a biologist at Louisiana State University in Baton Rouge, who
led the study. "We can measure all the chemistry we want in the environment, but
if want to know whether organisms have been exposed, we have to ask them."</P>
<P class=entry-content sizset="16" sizcache="4">The researchers studied the
impact of the 2010 Deepwater Horizon oil spill on Gulf killifish (<SPAN
class=i>Fundulus grandis</SPAN>) living in the Gulf of Mexico. They collected
water and tissue samples three times from marshes where the killifish lived:
once in early May, before oil from the blown well had arrived; once in late
June, when oil had reached the marshes; and again in late August, after oil was
no longer visible. They collected samples from six sites, but only one — in
Barataria Bay, Louisiana — was heavily oiled following the spill. </P></FONT>
<DIV class=inlineheading><FONT size=2 face=Arial><STRONG>Key
species</STRONG></FONT></DIV><FONT size=2 face=Arial>
<P class=entry-content sizset="21" sizcache="1">Whitehead has previously shown
that exposure to polychlorinated biphenyls (PCBs) can cause harmful gene
expression changes in killifish<SUP sizset="21" sizcache="1"><A
href="http://www.nature.com/news/2011/110926/full/news.2011.546.html?WT.ec_id=NEWS-20110927#B2">2</A></SUP>,
which are an important food source for many species, including economically
important ones such as red snapper. Because PCBs and the polycyclic aromatic
hydrocarbons (PAHs) found in crude oil have similar biological effects, the
researchers looked at their impact on the same set of genes. </P>
<P class=entry-content sizset="16" sizcache="4">They found analogous changes in
gene expression in killifish from the marshes, and in killifish embryos exposed
to contaminated water samples in the lab. These changes have previously been
shown to cause developmental abnormalities, decreased embryo survival and lower
reproductive success. "It doesn't take much PAH to mess with development,"
Whitehead says. </P>
<P class=entry-content sizset="16" sizcache="4">"The ability of fish larvae to
survive has a huge effect on the population down the road," says biologist Lee
Fuiman, director of the University of Texas Marine Science Institute in Port
Aransas, who was not involved with the study. "A small change in the percent
survival equals a large change in the adult population." </P>
<DIV class=inlineheading><STRONG>Persistent pollution</STRONG></DIV>
<DIV class=entry-content sizset="16" sizcache="4">
<P>In addition to the changes in gene expression, the effective surface area of
gill tissue was reduced, potentially impairing the ability of the fish to absorb
oxygen.</P><!-- end 300x250 ad -->
<P></P>
<P>Study co-author Fernando Galvez, also at Louisiana State University, is now
investigating how killifish embryos are affected by exposure to sediments from
the study's sample sites, which he says had concentrations of hydrocarbons that
were "through the roof". High concentrations of hydrocarbons in marsh sediments
can persist for years, continuing to expose organisms to their effects —
something that was seen long after the <SPAN class=i>Exxon Valdez </SPAN>spill
in Prince William Sound, Alaska, in 1989.</P>
<P>"The best predictors of long-term, population-level consequences after the
<SPAN class=i>Exxon Valdez </SPAN>spill were not dead animals in the water, but
sub-lethal effects," Whitehead says. "The same indicators that we're studying in
these killifish".<SPAN class=end-of-item> </SPAN></P>
<UL id=article-refrences class=xoxo sizset="16" sizcache="4">
<LI sizset="17" sizcache="4">
<H2 class=heading>References</H2>
<OL sizset="17" sizcache="4">
<LI id=B1 sizset="22" sizcache="1"><A name=B1><!-- . --></A>Whitehead, A.
<I>et al. </I><SPAN class=journalname>Proc. Natl Acad. Sci. USA</SPAN>
advance online publication <A class=reftxt
href="http://dx.doi.org/10.1073/pnas.1109545108">http://dx.doi.org/10.1073/pnas.1109545108</A>
(2011).</LI>
<LI id=B2 sizset="24" sizcache="1"><A name=B2><!-- . --></A>Whitehead, A.,
Pilcher, W., Champlin, D. & Nacci, D. <SPAN class=journalname>Proc. R.
Soc. B.</SPAN> <A class=reftxt
href="http://dx.doi.org/10.1098/rspb.2011.0847">http://dx.doi.org/10.1098/rspb.2011.0847</A>
(<SPAN
class=cite-month-year>2011</SPAN>).</LI></OL></LI></UL></DIV></FONT></BODY></HTML>