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Science

Jellyfish Swimming Is Mixing the Oceans 47

Posted by samzenpus
from the jellyfish-effect dept.
eviltangerine writes "A new article from LiveScience suggests that marine creatures, such as the jellyfish, may contribute as much to ocean mixing as wind and tides. Wired is also covering the story and includes a video of the jellyfish in action. From the article, 'The mere act of swimming implies that some water travels with the swimmer,' said CalTech engineer Kakani Katija, co-author of the study in Nature Wednesday. 'Drift applies to all animals, to anything with a body.' No word yet on when the jellyfish blender is to debut."
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Jellyfish Swimming Is Mixing the Oceans

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  • Ban the doggy paddle! It is a super effective mixing motion!
  • by Anonymous Coward

    "Drift applies to all animals, to anything with a body.' No word yet on when the jellyfish blender is to debut."

    Having been stung by a jellyfish the image of one in a blender did bring a smile to my face. They might make a nice sushi smoothie.

  • " 'The mere act of swimming implies that some water travels with the swimmer," said CalTech engineer Kakani Katija"

    Temporary vortices aside, I think that Sir Isaac Newton might take issue with this statement.

    • Agreed, End of discussion.

      • End of discussion.

        You don't want to join a discussion on membrane flappage and its effect on the aqueous continuum? Well, I guess that's up to you...

        ;-D
    • Re:Huh? (Score:5, Informative)

      by FlyingBishop (1293238) on Thursday July 30, 2009 @01:05AM (#28877803)

      At the very least, the organism contains water.

      However, Sir Newton shouldn't have any problem with the statement. Obviously, some water must be pushed away from the swimmer, but so long as the total water pushed backward equals the sum of the mass of the swimmer plus the sum of the water carried with the swimmer.

      Furthermore, once the Jellyfish is in motion, any water carried with it, like the Jellyfish, will want to continue in motion. The most low-energy state allows the water already in motion with the Jellyfish to continue moving, while water in front of the animal is pushed aside and around back.

      • Convoys (Score:1, Insightful)

        by Anonymous Coward

        Exactly. I mean isn't that why ships and trucks travel in convoys?

    • Re:Huh? (Score:5, Insightful)

      by Trepidity (597) <delirium-slashdot@@@hackish...org> on Thursday July 30, 2009 @01:06AM (#28877807)

      Unless the swimmer is frictionless, their sides drag some water along with them. Yes, water must be displaced backwards, but it's not false that "some water travels with the swimmer".

      • Re:Huh? (Score:5, Insightful)

        by Dunbal (464142) on Thursday July 30, 2009 @09:49AM (#28881245)

        Not a physicist but a physician. This makes sense - since it's roughly same way blood moves in blood vessels. Flow along the wall of the blood vessel is minimal. The greatest flow is in the center of the vessel, with diminishing flow the closer you get to the wall. That's why flow increases dramatically in larger blood vessels (it's a function of the fourth power of the radius - called the LaPoiseuille equation [wikipedia.org]).

              Again I'm no physicist, but I assume that if you have something pushing a fluid through a medium, you could define two boundaries that are not movable - the solid thing doing the pushing, and looking further and further out eventually you reach a "column" of water where the force does not get transmitted and is thus also static. Although it would be hard to get laminar flow in this scenario, it's not hard to imagine the greatest flow being generated where the greatest pressure change is - ie somewhere in the middle of the area described. The pressure change (and thus the flow) will be minimal where the static "walls" are, be they "real" (as in a solid fin, or an arm) or "not real" as in a non moving column of water.

    • Re:Huh? (Score:4, Informative)

      by Anonymous Coward on Thursday July 30, 2009 @01:15AM (#28877851)
      Then he must not understand fluid dynamics. When moving through a fluid, the fluid closest to the object moving moves very little or even not at all, implying that some gets dragged forward.

      Of course, a bunch gets flung back as well, which is what I assume you meant.
      • Sir Isaac Newton obviously had a swimming pool, which he skimmed himself. You do not. A body moving through the water creates currents.
        • by sumdumass (711423)

          I think what you are referring to as currents is the displacement of the liquid and the weight of the surrounding liquid pushing it back.

          However, the concept of water or liquid moving little around the object compared to more movement further away is a matter of friction and displacement. It gets a little more complicated to explain when you deal with buoyancy and displacement as other factors such as surface tension and gravity become involved but it's mainly a matter of friction. If you are neutrally buoy

    • Re:Huh? (Score:5, Funny)

      by TapeCutter (624760) * on Thursday July 30, 2009 @01:42AM (#28877963) Journal
      "Temporary vortices aside, I think that Sir Isaac Newton might take issue with this statement."

      Well yes if you put the vorticies (turbulance) to one side you have probaly eleminated the mode of travel for the water. Customary car analogy: If I take the wheels of my car it will no longer roll down hill.
  • not too surprising (Score:5, Interesting)

    by Trepidity (597) <delirium-slashdot@@@hackish...org> on Thursday July 30, 2009 @01:12AM (#28877843)

    The topic of ocean mixing is a huge subject [amazon.com], and seems to implicate just about everything you can think of: the atmosphere, geologic activity, emergent effects from complex system dynamics, boundary layers, energy dissipation, fluid turbulence, climate change, dissolved minerals, the rotation of the earth, gravitational effects of the moon, etc., etc. It's not particularly surprising to me that the actions of marine life are a significant component as well, though it's interesting to see actual numbers claiming to demonstrate it.

    • by j-stroy (640921) on Thursday July 30, 2009 @02:22AM (#28878165)
      The densities of sea life in the past is apparent in the history of its harvest. Were the oceans more prolific because of the amount of fish mixing? Mixing creates more interface, so wouldn't that affect tiny organisms because they get more exposure on the food chain?

      I recently read history of herring runs spawning in the Salish Sea [wwu.edu] so abundantly that the water was white, and that eggs were laid on everything in the water, such that they could be collected simply by submerging cedar branches. Not to mention historical quantities of fish all over the world...

      Just heard a flying astronaut again describing how thin a veil the atmosphere is and I realized that for how big a volume the earth is, its livable surface area(biosphere) isn't really that large at all. *duh* but I never connected spherical geometry (area vs volume) and the concept of how profoundly we could affect our environment when the earth is soo big.
      • Well, herring are primarily shallow water fish, and plankton ecosystems are as well, so I'm not sure that fish mixing is to blame so much as chronic over-fishing and pollution, or maybe that rather large hypoxic dead zone covering a significant percentage of the Oregon and Washington coastlines.

        The densities of sea life in the past is apparent in the history of its harvest. Were the oceans more prolific because of the amount of fish mixing? Mixing creates more interface, so wouldn't that affect tiny organi

        • by j-stroy (640921)
          I just wondered whether those formerly large populations were sustainable because of a factor like this, and once they were reduced beyond a point, the ocean became less "fertile", causing an additional downward pressure...
    • "...and seems to implicate just about everything you can think of: the atmosphere, geologic activity, emergent effects from complex system dynamics, boundary layers, energy dissipation, fluid turbulence, climate change, dissolved minerals, the rotation of the earth, gravitational effects of the moon, etc., etc..."

      You forgot Sea Cow farts.

      http://en.wikipedia.org/wiki/Sea_Cow [wikipedia.org]

  • A neglected factor (Score:2, Insightful)

    by fucket (1256188)
    6 percent of ocean mixing is caused by the thrashing of swimmers in the process of being devoured by great white sharks. 18 percent of these are being eaten by the same shark that killed their father.
  • by Anonymous Coward

    Let's All Go Jellyfishing!!! (This is the Best Day Ever!!!)

  • by p!ngu (854287) on Thursday July 30, 2009 @03:01AM (#28878375)

    Science: Jellyfish Swimming Is Mixing the Oceans

    eviltangerine writes

    "A new article from LiveScience suggests that marine creatures, such as the jellyfish, may contribute as much to ocean mixing as wind and tides.

    I mean, I know headlines can't convey everything, but it seems a few leaps have been made...

  • Like Slashdot not SlashDot... now that wasn't hard was it?

  • I'll have a Martini James.
    Pulsated, not stirred!
  • which is definitely worth checking out. [npr.org] Really amazing stuff!

    The BBC [bbc.co.uk] story also has some interesting points about why jellyfish in particular are being looked at.

  • That's like saying the movement of animals affect the wind. Let me guess, birds were once so populous that the beating of their wings....what bullshit. Sounds kewl tho...you know, the kind of cool that's so stupid it's interesting?

To err is human -- to blame it on a computer is even more so.

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