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Selasa, 08 November 2011

HAIR O' THE SEAL

Antarctic fur seal (right), Weddell seal (left), Penguin Island, South Shetland Islands, Antarctica. Credit: � Julia Whitty.
   
How do you assess the health of a marine invertebrate�namely Antarctic krill�when there's no historical baseline to measure it against? 

In an intriguing piece of detective work reported in PLoS ONE a team of researchers from China and the US turned to analyzing old seal hairs to determine changes in abundance of krill in the past century.

Antarctic krill. Credit: Uwe Kils via Wikimedia Commons.

Antarctic krill, Euphausia superba, is a keystone species in the Southern Ocean and the primary consumer in a foodweb supporting fish, penguins, seabirds, seals, and whales. 

They school in swarms of up to of 30,000 individuals per cubic meter and are perhaps the most abundant animal on Earth, with a total biomass estimated at ~379 million metric tons.

In the video below (starting at 00:01), you can see humpback whales bubble feeding on krill in Antarctic waters.
 

There's evidence of a decline in krill biomass in parts of Antarctica in the past 30 years�but when did it begin?

To look deeper into history, the authors analyzed core samples from lake sediments near an Antarctic fur seal colony on King George Island in the South Shetland Islands off the Antarctic Peninsula.They dated the fur in the cores via stable carbon (d13C) in the samples. They inferred the abundance of krill in the seals' diet via the nitrogen (d15N) isotopes in the fur. From the paper:

Since Antarctic fur seals feed preferentially on krill, the variation of [nitrogen] in seal hair indicates a change in the proportion of krill in the seal's diets and thus the krill availability in local seawater.
  
Antarctic krill grazing on algae living on the underside of sea ice. Credit: Uwe Kils via Wikimedia Commons.
  
Their results indicate that krill began to decline in the diet of fur seals in this part of Antarctica nearly a century ago. That time frame correlates with increasing sea surface temperatures and dwindling sea ice. (See my post Life Inside the Sea Ice more about the relationship between krill and sea ice.) 

From the PLoS ONE paper:

In this region for the past decades, the sea ice shows a decline trend, and this is in coincidence with the decline trend in krill populations. Like the seal [nitrogen] values, the sea surface temperature anomaly in Southern Ocean (50�S) also shows an obvious increasing trend for the 20th century, and the significant correlation between them... suggests that the inferred decreasing krill population is linked with warming ocean and declining sea ice extent.
 


The paper: 

  • Huang T, Sun L, Stark J, Wang Y, Cheng Z, et al.Relative Changes in Krill Abundance Inferred from Antarctic Fur Seal.PLoS ONE. 2011.DOI:10.1371/journal.pone.0027331.

    Rabu, 02 November 2011

    ANTARCTICA EMERGES

    1657. Jan Janssonius. Dutch. Showing hints of southern coastlines labelled 'Terra Australis Incognita.'

    1714. French. Guillaume de L'Isle. Antarctica empty.

    1739. Philippe Buache. French. Showing two Antarctic land masses, New Zealand connected to Antarctica, and Australia connected to New Guinea.

    1777. Thomas Bowen. British. Showing the 'Track of his Majesty's Sloop
    Resolution in Search of a Southern Continent.'

    1818. John Pinkerton. US. Antarctica missing again.

    1855. J. H. Colton. US. Showing partially sketched details of the 'Southern Regions.'

    1894. Scottish. Real features getting named, including ocean currents.

    1912. German. From Stielers Handatlas. Suddenly, details.

    1920s. Showing 'unexplored regions,' focus on expedition routes.

    1922. John Bartholomew. UK. Limited but exquisite detail.

    1934. US. Focusing on the Byrd Expedition.

    1972. H.C. Berann. US. Showing Antarctica in context with the seafloor.

    2006. UK. Showing Antarctica without the ice.

    2006. Dave Pape. Stitched satellite view.

    Rabu, 08 Juni 2011

    HAPPY WORLD OCEAN DAY

    (Weedy sea dragon, Phyllopteryx taeniolatus. Credit: Richard Ling, Rling via Wikimedia Commons.)

    In case in the middle of an ordinary dry Wednesday you've forgotten how extraordinary is our ocean planet, here are a few watery reminders.


    The Blue Ocean in RED from Howard Hall on Vimeo.

























    (Squid, possibly the bigfin reef squid, Sepioteuthis lessoniana. Credit:Nhobgood at Wikimedia Commons.)



    MAYO / MAY from Rafa Herrero Massieu on Vimeo.

























    (Giant anemone, Condylactis gigantea. Credit:Nhobgood via Wikimedia Commons.)


    Antarctica from Darek Sepiolo on Vimeo.

























    (Kelp. Credit: FASTILY via Wikimedia Commons.)




    This new product released by Google Earth and developed by oceanographers at Columbia's Lamont-Doherty Earth Observatory promises a dynamic look through darkness to the seafloor. I confess, the extinct filmmaker in me wants to get my hands on this video and edit in some heft. But you can see how cool the perspectives are�how the new layers make Google Earth more oceanlike.

    (Great white shark, Carcharodon carcharias. Credit: Pterantula via Wikimedia Commons.)

    Jumat, 19 November 2010

    MYSTERY OF THE ICE WHALES
























    (The whale within the iceberg. 1884. By George R. Halm. From the New York Public Library Digital Gallery.)

    Believe it or not, whales sometimes end up frozen in glaciers, some of which may then calve out with icebergs to float around the ocean for a spell. 

    The illustration above, by New York artist George R. Halm (1850-1899), tells a visually compelling story�though the words to this tale have been forgotten, as best I can tell.












    So what could the picture be about? Well, the engraving includes images of men at work on the sea. Maybe whalers.









    Handwritten at the bottom of the print is the word "Whaling"�perhaps a catalogue notation from an early librarian.















    The detail in the lower left might be an image of a sunken ship. Maybe a whale-wrecked ship. With nothing left afloat but the crow's nest? I'm not sure. Was there once a story of a wronged whale and a haunted iceberg on an intercept course with a few doomed sailors?

    Moby Dick was published 33 years before George R. Halm's engraving�priming the public mind for tales of vengeful behemoths.



    moby dick intro from Carys Banks on Vimeo.

    Interestingly, in his description about the the blubber of sperm whales, Herman Melville included an eerie reference to ice seamen:

    For the whale is indeed wrapt up in his blubber as in a real blanket or counterpane; or, still better, an Indian poncho slipt over his head, and skirting his extremity. It is by reason of this cosy blanketing of his body, that the whale is enabled to keep himself comfortable in all weathers, in all seas, times, and tides. What would become of a Greenland whale, say, in those shuddering, icy seas of the North, if unsupplied with his cosy surtout? True, other fish are found exceedingly brisk in those Hyperborean waters; but these, be it observed, are your cold-blooded, lungless fish, whose very bellies are refrigerators; creatures, that warm themselves under the lee of an iceberg, as a traveller in winter would bask before an inn fire; whereas, like man, the whale has lungs and warm blood. Freeze his blood, and he dies. How wonderful is it then�except after explanation�that this great monster, to whom corporeal warmth is as indispensable as it is to man; how wonderful that he should be found at home, immersed to his lips for life in those Arctic waters! where, when seamen fall overboard, they are sometimes found, months afterwards, perpendicularly frozen into the hearts of fields of ice, as a fly is found glued in amber.







    For another ice whale story only slightly less mysterious, I found a 1959 paper in Nature, about the 1958 discovery of a whale entombed in a glacial moraine beyond which the glacier had retreated in Svalbard (also known as Spitzbergen), north of mainland Norway.


    (The Isefiorden, Spitzbergen, Norway, c. 1890-1900. From the Library of Congress' Flickr photostream.)

    Disappointingly, I can only read the abstract, since even with my exorbitantly expensive personal subscription to Nature I am not entitled to read back issues from 1959. (O, ?less policy.)

    The abstract is tantalizing:

    THE preservation of Pleistocene or Recent land mammals in the Siberian permafrost has long been known, but the literature does not appear to include mention of marine mammals preserved in ice. Particular interest, therefore, is attached to the discovery in 1958 of part of a whale carcass entombed in the ice-cored moraine of Sveabreen, Ekmanfjord, in Vestspitsbergen. The north-eastern lateral moraine of Sveabreen projects into the fjord about two miles beyond the ice-front, and the find was made by members of the Birmingham and Exeter Universities Spitsbergen Expedition near the seaward tip.
























    (Bowhead whale. Photo by Ansgar Walk, courtesy Wikimedia Commons.)

     What species of whale was it? Were they able to determine? 

    There was a huge whaling and walrusing industry in Svalbard beginning in 1604�a piratical affair between British, Dutch, Danish, and French mercantile companies, who built forts to defend their commercial interests.

    (Photo from the BBC.)

    Their primary targets were bowhead whales�the real ice whales.


    (The whale-oil factory of the Amsterdam Chamber of the Greenland Company on Amsterdam Island near Spitzbergen. 1639. Cornelis de Man.)

    In 1996 a bowhead whale melted out from another Svalbard glacier, bringing with it a few juicy clues about its past... including a death date circa end of the Little Ice Age... perhaps from the time of the earliest commercial whalers.

    Here's the abstract of the 1997 paper in Polar Research:

    An 8 m long carcass of a bowhead whale (Balaena mysticetus) melted out from remnant glacier ice in the lateral moraine of the Jemelianovbreen glacier in August 1996. Folded and sheared sediment bands in the ice suggest that the whale was incorporated during an advance of the glacier. The whale's longitudinal axis was oriented parallel to the direction of the ice-flow, with the thinnest posterior part dipping upflow. The posterior section was best preserved with muscles and blubber, although the entire skin surface was strongly decomposed and only a thick fibrous surface was left of the blubber. The abdominal wall was holed, most likely by marine organisms, and partly filled with a compacted mixture of well-sorted gravelly beach sediments and fat. the whale seems to have been incorporated into the glacier together with glaciomarine sediments and carried by the flowing ice to an altitude of ca. 15 m. Jemelianovbreen is a tidewater glacier with two known surge-episodes. The first and most extensive of these occurred ca. 1900 AD and reached ca. 7 km outside the present coast-line. Radiocarbon dating of a fragment of a caudal vertebra yielded 345 � 40 14C years BP (1535-1660 cal. AD), suggesting that the whale lived some time during the last part of the cold period known as the Little Ice Age.

    (Antarctic toothfish, Dissostichus mawson, a Nototheniid. Photo by Paul Cziko, courtesy Wikimedia Commons.)

    Whales aren't the only mysteries trapped in ice. A 1962 paper in the Polar Record recounted all kinds of entombed marine life found by early Antarctic explorers. The abstract:

    In February 1902, members of Scott's Discovery expedition found the remains of a fish 18 in. long on the surface of the "pinnacled ice" near the ice front of the Ross Ice Shelf in McMurdo Sound. In 1903, a party under Wilson found three Nototheniid fishes, sponges, shells, and seaweeds among similar ice on the floating section of the Koettlitz Glacier. The fishes, which were up to 48 in. in length, were all headless. They resembled a specimen caught in a seal blow-hole near the Discovery winter quarters, whose head was bitten off by a seal before it could be landed, but whose body weighed 40 Ib. and was 46 in. long. This fish was a Notothenia, close to N. colbecki Boulenger. In 1911, a party under Taylor found another large headless fish, which may have been as much as 4 ft. long, embedded in the ice of the Lower Koettlitz Glacier some 5 miles from its seaward end, and among the pinnacled ice near the Dailey Islands the same party found corals, shells, sponges, patches of sediment, and about a dozen small fish. The ice in this region was so rich in sponges that it was difficult to get spicule-free ice for cooking.



    (The pinnacled ice of McMurdo Sound, photographed by Reginald Skelton for the British National Antarctic Expedition�aka Scott's Discovery expedition�1901-1904. From the Royal Collection.)

    A news story out of Greenland in 1985 aroused the mystery again, along with a new round of theorizing:
    A dead whale frozen in an iceberg 13 feet above the surface of the frigid waters off south Greenland is mystifying scientists and curious residents of a tiny Greenland settlement. No one can figure out how the 59-foot sperm whale died or how it ended up in an icy grave high above the water drifting a few miles off the tiny settlement of Alluitsup. First came speculation the beast was a prehistoric creature buried for eons in the ice cap that makes up 85 percent of Greenland. But examination showed that the whale, the size of which indicates it was a male, was identical to contemporary sperm whales. And it emitted a rank smell, making fossilhood unlikely... Close inspection reveals the whale may have been the victim of a hunter`s harpoon. In its neck is a cylindrical hole 15 inches in diameter and three feet. But that does not explain how the beast came to rest in an icy grave bobbing 13 feet above the water. One theory is that it sprang into the air and landed unluckily on a large iceberg, perhaps stuck in a narrow crevice. Marine biologists in Greenland theorize the whale may have been attacked by killer whales, or, stranded in a shallow area, became disoriented and died. They believe the whale, weakened or dead, could have drifted over the submerged portion of an iceberg and become an involuntary hitchhiker when the iceberg separated and a submerged portion rose under the whale.


    Cutting Room Floor: "Deep at Sea" from Tristan Bayer on Vimeo.

    (The filmmaker describes: "This cut is made with unused footage that we shot in Dominica which would otherwise be left on the 'Cutting Room Floor.''')

    The papers:

    Rabu, 23 Juni 2010

    OUTTAKES: ANTARCTICA


    For a long time I had a sizable Antarctica section in the manuscript for my book DEEP BLUE HOME. But it didn't survive round two of my own cuts. Which doesn't mean I didn't like it. I prefer to think of a cut as a postponement, and remain hopeful the piece will a find a home in a future book.

    Some of my favorite parts of DEEP BLUE HOME that made it through to publication came from an old novel I was working on a few years back. Recycling (I call it parasitizing) my own work makes me happy.

    Here's a taste of the Antarctica outtake:
    At first glance, the massive penguin rookery at Brown Bluff looks to be strewn with the carcasses of penguin chicks. Thankfully, they�re not dead, only prostrate with heat�so fat and absurdly fuzzy that they�re forced to lie prone on rotund krill bellies, wings outstretched, webbed feet raised in the air behind them, shedding heat through the only unfeathered parts of themselves. The Ad�lie chicks hatched earlier than the Gentoos on the island and some are near fledging now, emerging from their down feathers like penguins from gorilla suits. Most are joining cr�ches and partaking in the comical affairs known as feeding chases: a parade of chicks besieging any parent returning from the sea, the youngsters chattering loudly of their hunger. The returning parent, bloated with krill, lurches as fast and far away as it can, hoping to winnow its own chick from the mob. Some feeding chases persist a thousand feet down the beach, a long way for birds with no ankles.




    (Photos � Julia Whitty)

    Rabu, 31 Maret 2010

    ANTARCTICA UNDERWATER



    Huge forests of nasty-tasting kelps, plus soft corals, sponges, tunicates, and really really cold water.