Increasing numbers of invasive species of seaweed are arriving on Rhode Island shorelines every year, potentially resulting in negative effects on tourism and the local economy, according to local researchers.

To keep track of these invaders and to document all of the native seaweed species in the region, scientists and students from the University of Rhode Island and Roger Williams University are conducting a statewide seaweed census and creating an online seaweed DNA database to track changes in biodiversity.

“We’re essentially using seaweed as a sentinel to monitor the health of the coast,” said Christopher Lane, URI assistant professor of biological sciences.  “By keeping tabs on what’s going on in the seaweed community, you can get a good idea of what’s happening throughout the marine environment.”

The seaweed census is especially timely because of the recent arrival of Heterosiphonia japonica, an aggressive, red feather-like seaweed native to Japan that was reported in Rhode Island in 2010 and is smothering and replacing native seaweeds throughout the coast.

“It grows right on top of everything else and could become a major problem,” Lane said. “It can form large mats on the seafloor, and when it becomes detached it washes up in large quantities on beaches. It also has the potential to clog aquaculture facilities.  Since it has no natural herbivore around here, it’s just running rampant.”

Lane said that when new species arrive in an environment there is always a period of instability, and there is little that can be done but wait until nature gets back into balance. “Unfortunately, the transition might not be pleasant,” he said.

In addition to monitoring invasive species, Lane said the seaweed census also aims to identify changes in biodiversity caused by climate change.

“One thing we’re looking for is examples of seaweeds that are mediated by sea surface temperature,” he said.  “Some species can’t reproduce if temperatures get too warm, so we’re keeping an eye on the water temperature to see how seaweeds are reacting to it. We could end up seeing a change in species composition.”

The seaweed census began this spring and will continue throughout the year.  Lane and his students are surveying the West Bay and South Coast regions, while Roger Williams University associate professor Brian Wysor is leading the effort in the East Bay. They walk beaches at low tide to collect samples, and don scuba gear at high tide to search the intertidal zone and areas just off shore.

The samples they collect are permanently archived, and a DNA sample from each species is stored in a database. The data will be shared with scientists undertaking a similar project for the entire New England region.

One of the challenges the scientists face is that it’s extremely difficult to identify many seaweeds by the way they look.

“There are a lot of instances when there are two seaweeds that look the same but are very different, or two that look very different but are the same species,” Lane said. “We’re trying to get a handle on how many fit into those categories so we know whether we’re overestimating or underestimating how many species we have.”

One outcome Lane expects at the end of the project is the identification of seaweed species completely new to science. A similar census he conducted in Bermuda during the past 10 years found 70 new species.

The project is being funded by a grant from the Rhode Island Science and Technology Advisory Council.