Scientists at the University of Bremen in Germany reported even less ice this summer than the NSIDC. Scientists blame rising temperatures for the drop in sea ice levels. They say ocean temperatures are rising around the world.

In recent years, the record low sea ice levels forced walruses to seek food and rest along the northwest coast of Alaska. But scientists fear there may not be enough food so close to the coast.

Thousands of walrus are congregating on Alaska's northwest coast because of receding sea ice in the Arctic

BOB DOUGHTY: More than twenty thousand walruses crowded onto the coastline earlier this year. The overcrowded conditions put younger smaller walruses at risk of being crushed. More than one hundred thirty walruses died during similar conditions in two thousand nine.

Some scientists have warned that, if temperatures continue rising, Arctic sea ice may disappear completely by twenty thirty. They say this would threaten walruses and the whole ecosystem in the Arctic Ocean.

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BARBARA KLEIN: Piranhas are known as dangerous, meat-eating fish. However that did not stop scientists in Belgium from working with them to learn more about the sounds these unusual fish make.

There are more than twenty different species of piranhas in the wild. Two or three of them are a threat to humans. Among them are the red-bellied piranhas. The scientists knew that red-bellied piranhas produce sounds. However it was not clear when or why they make these sounds. So a team of scientists studied red-bellied piranhas to learn more about how they communicate. The head of the team was Eric Parmentier from the University of Liege.