Recent research has shown that protecting loggerhead sea turtles should be an international issue.
By using DNA fingerprinting, scientists from the universities of Florida and Lyon found that 57% of Mediterranean juvenile loggerheads had hatched on eastern U.S. beaches. The turtles, carried across the Atlantic by the Gulf Stream, may spend up to 20 years in the Mediterranean. Then, through genetic cues, they return to U.S. beaches, where nesting has been declining. Declining numbers of loggerhads had been linked to western Atlantic over-exploitation. Now, it's understood that the 20,000-50,000 loggerheads killed annually as unwanted catches in the Mediterranean swordfish fishery may be the cause.
Scientists have discovered a type of fast-moving eddy (or whirlpool) that forms 1000 m below the Mediterranean's surface and moves into the Atlantic. These Mediterranean eddies, or "meddies," may be 100 km in diameter and extend about 800 m vertically. The water in their cores is as much as 4 C warmer and 1 part per thousand saltier than surrounding water. Meddies are long-lived and can travel far while retaining their physical characteristics (mostly due to rapid rotation). One meddy tracked for 2 years traveled about 2000 km.
How and why meddies form, and how many meddies form each year, remain to be learned.
Bathtub toys--over 29,000 plastic turtles, ducks, beavers, and frogs--became scientific instruments when a severe storm dumped them overboard into the Pacific on January 10, 1992. Ten months later, the toys began turning up on beaches near Sitka, Alaska.
By compiling data on where the toys were found, researchers have added to understanding of Pacific drift patterns. By the end of the century, toys are expected to be dispersed around the Arctic, North Pacific, and northern North Atlantic.
In September 1993, salt content of waters off Florida fell from the usual 36 parts per thousand to 31 ppt. Scientists thought the drop might be due to instrument error, but later (by measuring isotopes, zooplankton species, and drifters) recognized that it was caused by massive Mississippi River flooding earlier in the year.
Water coming into the Gulf of Mexico from the Mississippi normally flows towards Texas. This time wind changes carried the diluted water toward the Gulf Stream. This "river" of lower salt content was nearly 15 miles wide and 70 feet deep as it flowed past the Florida Keys.
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gene carl feldman (gene@seawifs.gsfc.nasa.gov) (301) 286-9428 Judith Gradwohl, Smithsonian Institution (Curator/Ocean Planet)