Oceanography The Official Magazine of
The Oceanography Society
Volume 20 Issue 04

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Volume 20, No. 4
Pages 16 - 19


RIPPLE MARKS • Winter Ice on Lakes, Rivers, Ponds | The Tales Melting Ice Could Tell | Clams Make Food from Thin Air | Out-Swimming an Estuarine Crocodile

By Cheryl Lyn Dybas  
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Winter Ice on Lakes, Rivers, Ponds

Going, going, gone? If you're planning to ice skate on a local lake or river this winter, you may need to think twice, according to scientists John Magnuson, Olaf Jensen, and Barbara Benson of the University of Wisconsin at Madison and their colleagues. From sources as diverse as newspaper archives, transportation ledgers, and religious observances, the researchers have amassed 150 years of lake and river ice records spanning the Northern Hemisphere. Almost all show a steady trend of fewer days of ice cover.

The Tales Melting Ice Could Tell

 "Valleys of the dead," Antarctic explorer Captain Robert Falcon Scott called them in 1905. Indeed, Antarctica's Dry Valleys are among the most desolate places on Earth. The ice-covered moonscapes seem freeze dried and completely lifeless. But scientists Kay Bidle, SangHoon Lee, and Paul Falkowski of Rutgers University in New Brunswick, New Jersey, and David Marchant of Boston University, have found that these glacier-covered landscapes harbor tiny frozen organisms that have remained "alive" for more than a million years, encased in the oldest ice on Earth.

Clams Make Food from Thin Air

Only plants can take nitrogen gas from the air and use it to make the protein they need to grow. Or so biologists thought. Now scientists at Ocean Genome Legacy in Ipswich, Massachusetts, and their colleagues at Harvard Medical School have shown that animals, too, can convert food into air. The animals are marine clams called shipworms. They burrow into and eat wood, causing more than a billion dollars in damage to ships and piers each year.

Out-Swimming an Estuarine Crocodile

Don't try this at home. Estuarine crocodiles, Crocodylus porosus, have a remarkable ability to find their way home, even across great distances, said biologist Craig Franklin of the University of Queensland in Australia. He and colleagues describe in a September 2007 paper in the journal PLoS ONEhow they caught and tagged three large male "salties," as Franklin refers to them, transported the crocs 59, 99, and 411 kilometers, respectively, along the Australian coastline, then tracked their movements via satellite telemetry.


Dybas, C.L. 2007. Ripple marks—The story behind the story. Oceanography 20(4):16–19, https://doi.org/10.5670/oceanog.2007.20.

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