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Rat populations affect shoreline ecosystem, shrimplike krill found at new depths, worms show traces of personal-care products.

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Wild Thing: Scientists have discovered that the tiny shrimplike krill. a key food source for larger marine creatures, migrate to depths of up to 10,000 feet.

Melanie Stetson Freeman – staff

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Rats' drastic effects on islands

Rats have a reputation for avoiding water. But that doesn't prevent them from profoundly altering marine ecosystems.

Norway rats on the Aleutian Islands have drastically changed the type of organisms living along the shores between the high and low tide marks. They've done so by decimating the number of shorebirds that feed there, according to two scientists at the University of California at Santa Cruz.

The duo conducted field studies between 2002 and 2005 on 23 islands spread throughout the Alaskan archipelago. Eight islands had large rat populations, thanks to shipwrecks as early as the 1700s; 15 islands were virtually ratless. The scientists found that on the rat-infested islands, the rats had raided the birds' nests, eating the eggs and chicks. Without birds to control their numbers, snails and limpets proliferated and munched away at the seaweed dominating the shore between high and low tide marks. Mussels and sea stars replaced the seaweed on the rocky shoreline. On the rat-free islands, where birds flourished and dined on invertebrates, the intertidal zone remained dominated by seaweed.

The study highlights how invasive species can have landscape-wide effects beyond the immediate impact they have on the species they wipe out. The results appear in this week's issue of the Proceedings of the National Academy of Sciences.

Tiny krill are deep-sea divers

For the first time, scientists have found tiny shrimplike krill at depths of up to 3,000 meters (nearly 10,000 feet) off the Antarctic coast. Krill serve as the main course for squid, whales, penguins, and other marine creatures. Up to this point, krill were thought to hang out within 150 meters (500 feet) of the ocean surface. The results will force scientists to overhaul their ideas about krill habits and ecology, say two British Antarctic Survey scientists who discovered the deep-diving krill.

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