The Oshoro Maru in port on July 23, 2013. (Audrey Carlsen/KUCB)

The R/V Oshoro Maru stopped by Unalaska to refuel on Tuesday after spending three weeks in the Arctic. While they were in port, several of the onboard scientists hopped off to talk about their research.

The 239-foot ship is a regular visitor to Unalaska because of its affiliation with UniSea’s Japanese parent company. The ship is owned by Hokkaido University, where many of the 45 scientists aboard work. This summer, they were in the Bering and Chukchi Seas researching a variety of topics, including plankton and seabird migration, and testing a new underwater remote-operated vehicle.

Yoko Mitani is an assistant professor at Hokkaido University, and was one of four researchers who gave talks about their work. "[The] purpose of the study is we want to know the sea ice decline impacts to marine mammals," she says.

Her hypothesis is that as sea ice recedes, migratory mammals like killer whales will be able to spend more time in the far north. That could put a strain on limited Arctic resources, and Mitani thinks it could have big consequences for the food chain.

"Marine mammals [are] a top predator of the ecosystem," says Mitani. "So top-down effects may affect the whole ecosystem."

Mitani’s research team is monitoring the locations of marine mammals using acoustic buoys -- basically eavesdropping under the ice. They can identify the unique sounds that different species make underwater from up to three miles away.

This is Mitani’s second year collecting data, but it will take several more years to yield any meaningful results. She and several of the other researchers plan to be back next year. But when they pull into port again, it'll be aboard a different ship. The Oshoro Maru is being retired and will be replaced by a new ship to continue transporting researchers up to the Arctic -- and to Unalaska.