On the horizon: News from the frontiers of science
Rat populations affect shoreline ecosystem, shrimplike krill found at new depths, worms show traces of personal-care products.
Melanie Stetson Freeman – staff
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.
The scientists say they were amazed to find adult krill, including pregnant females, feeding at such great depths. Video from a remotely-controlled vehicle shows the krill smacking headfirst into the muck on the seafloor, then swimming back through the cloud of material they kicked up to eat the nutrients in the cloud.
These krill probably don't represent an undiscovered population, the two say. Instead, the krill appear to migrate up and down the water column. The results appear in this week's issue of the journal Current Biology.
Worms absorb human pollutants
Beware the earthworm wearing Chanel No. 5. Scientists at the University of Colorado at Pueblo, Eastern Washington University, and the US Geological Survey have for the first time found earthworms in the field bearing traces of a range of compounds used in personal-care products, including perfumes, as well as medicines used by people and livestock.
Other studies have reported that earthworms accumulate contaminants. But this is the first major evidence outside the lab, the team says.
Over the years, concerns have grown about the effects of drugs and cosmetics in liquid effluent from treatment plants on aquatic and marine life. The higher up the food chain a compound migrates, the higher the levels of these chemicals researchers find in top level predators.
The path from people to soil travels through sewage-treatment plants that sell the treated solids as manure or fertilizer to small farms or large-scale land-reclamation projects, according to the scientists.
The researchers not only are interested in the effects the accumulating chemicals have on earthworms themselves, but on the animals that feed on the worms. The results appear in a recent issue of the journal Environmental Science and Technology.