PORTLAND – A team of 25 scientists surveying piers, docks and coves on the region’s coast for invasive pests is documenting the growing problem of sea squirts as well as a newcomer, red alga, that’s been spreading in southern New England.

The scientists wrapped up their weeklong survey Saturday by inspecting a cove and two marinas in Cape Elizabeth, South Portland and Freeport. Earlier in the week, the team visited sites in Rhode Island, Massachusetts and New Hampshire.

The goal is to develop a baseline inventory of marine animals and plants that have taken up residence in ocean waters where they don’t naturally occur and determine if they pose threats to native organisms. The European green crab and the Asian shore crab, for instance, prey on commercially valuable shellfish, while other invasive species have been known to damage piers and pilings.

The worst group in recent years has been sea squirts, or tunicates, which are spreading across New England, said Jan Smith of the Massachusetts Office of Coastal Zone Management.

“They’re like a creeping mass and smother other things,” he said. “We’re finding it virtually everywhere and it’s smothering native communities.”

This is the fourth time since 2000 that scientists have surveyed the New England coastline to collect information on ocean invaders. The survey is coordinated by the MIT Sea Grant program, the Massachusetts Bays Program and the Massachusetts Office of Coastal Zone Management, with assistance from estuary programs in different states.

There are at least 64 plants and animals, ranging from sea anemones to barnacles and crabs, that are not native to the region and can now be found in New England waters, Smith said.

This year’s project brought together a team of scientists from the United States, Canada, Brazil and the Netherlands who have taken samples at marinas and along the shore and examined their findings in laboratories.

Scientists this year have seen a red alga spread in southern New England, Smith said. The alga, which is native to the Pacific Ocean, first showed up three years ago in Narragansett Bay, but has yet to cause any problems.

Scientists also came across a sponge-like organism on a dock near Newport, R.I., that they couldn’t identify, he said.

The survey is important because it provides information about species that could hurt both the ocean and those who make a living off of it, said Curtis Bohlen, director of the Casco Bay Estuary Partnership, which provides assistance to the survey.

Off Maine, sea squirts increasingly have been showing up on the ocean floor and growing on lobster traps that are set along the coast, Bohlen said.

“My concern is as these things are coming in, they’re rearranging our marine ecosystem in ways we don’t really understand,” Bohlen said. “The potential risk to the way we make a living in Maine’s marine environment is significant, and we’d like to know that before it becomes a problem.”