Marine life in Antarctica may be threatened by floating plastic.

Scientists have always believed Antarctica was isolated from the rest of the world - until huge bits of seaweed washed up.

Research by a team from the University of Otago found the kelp had drifted 20,000 kilometres from the Kerguelen Islands to reach Antarctica.

Professor John Waters says if seaweed can make it to Antarctica, so can things like plastic.

"This gives us some real worries that even Antarctic waters are not going to survive plastic free, with the huge amount of garbage that is infesting our oceans."

Professor Waters also says the plastic problem is another level of worry for marine life in the area, and it's changing the way researchers look at the Antarctic ecosystem.