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<DIV>Nature </DIV>
<DIV>Volume 460 Number 7255 pp 551-658</DIV>
<DIV>30 July 2009 </DIV></FONT>
<DIV class=page-header> </DIV>
<DIV class=page-header><FONT size=3><STRONG>Editor's
Summary</STRONG></FONT></DIV>
<DIV id=cite> </DIV>
<DIV id=atl><FONT size=4>Marine animals cause a stir</FONT></DIV>
<P class=norm>An all-but forgotten contribution of Sir Charles Darwin —
physicist grandson of the Charles Darwin — has resolved a long-standing debate
about ocean mixing. He suggested, in 1953, a mechanism that enables swimming
animals to contribute significantly to the mixing of water in the ocean. The
debate about the biogenic mixing in the oceans today focuses on comparisons
between animal wake turbulence and ocean turbulence. 'Darwinian' mixing is
different, and occurs when a solid body travelling in a fluid sets a portion of
the surrounding fluid into motion so that it propagates along with the body.
Kakani Katija and John Dabiri used field measurements of jellyfish swimming in a
remote island lake, combined with a new theoretical model, to demonstrate that
<U>the contribution of living organisms to ocean mixing via this mechanism is
substantial — of the same order of magnitude as winds and tides.</U></P>
<P class=norm>*************************************************</P>
<H3 class=listing><SPAN class=atl>Oceanography: A fishy mix</SPAN></H3>
<P class=abs>Ocean life is in almost constant motion, and such activity must
surely stir things up. Innovative investigations into this concept of 'biogenic
mixing' show a role for jellyfish and their brethren.</P>
<P class=aug>William K. Dewar</P>
<P class=doi><SPAN class=doi><ABBR
title="Digital Object Identifier">doi</ABBR>:10.1038/460581a</SPAN></P>
<P class=links><A class=fulltext title=""
href="http://www.nature.com/nature/journal/v460/n7255/full/460581a.html">Full
Text</A> | <A title="PDF (667K) of "
href="http://www.nature.com/nature/journal/v460/n7255/pdf/460581a.pdf"><ABBR
title="Portable Document Format">PDF</ABBR> (667K)</A></P>
<P class=links>*********************************************************</P>
<H3 class=listing><SPAN class=atl>A viscosity-enhanced mechanism for biogenic
ocean mixing</SPAN></H3>
<P class=aug>Kakani Katija & John O. Dabiri</P>
<P class=doi><SPAN class=doi><ABBR
title="Digital Object Identifier">doi</ABBR>:10.1038/nature08207</SPAN></P>
<P class=links><A title=""
href="http://www.nature.com/nature/journal/v460/n7255/abs/nature08207.html">First
paragraph</A> | <A class=fulltext title=""
href="http://www.nature.com/nature/journal/v460/n7255/full/nature08207.html">Full
Text</A> | <A title="PDF (418K) of "
href="http://www.nature.com/nature/journal/v460/n7255/pdf/nature08207.pdf"><ABBR
title="Portable Document Format">PDF</ABBR> (418K)</A> | <A
title="Supplementary information: "
href="http://www.nature.com/nature/journal/v460/n7255/suppinfo/nature08207.html">Supplementary
information</A></P></FONT></BODY></HTML>