UVI researchers studying invasive sea grass

UVI researchers studying invasive sea grass
BY ALDETH LEWIN (DAILY NEWS STAFF)
Published: January 18, 2015

ST. THOMAS - An invasive species of sea grass is taking over the waters of St. Thomas and St. John, and researchers are trying to figure out what - if anything - eats it.

It seems to be spreading quickly, according to University of the Virgin Islands Marine and Advisory Service coordinator Howard Forbes Jr.

The new species is Halophila stipulacea, and while it is smaller than the native sea grasses, it is taking over and pushing out the native species.

"It's much smaller in size in comparison to the other species of sea grass that we have here, it just happens to grow really, really well," Forbes said.

This is a problem because many underwater creatures depend on the native grasses for food and protection and scientists are worried about what could happen to the island's ecological systems if the native sea grasses disappear.

Halophila stipulacea is native to the western Indian Ocean and is thought to have spread into the Mediterranean and Caribbean seas in ship ballasts.

The way the grass reproduces is through fragmentation. If a piece breaks off, it starts growing a new plant.

Forbes said this is believed to be the reason it is spreading so fast. Every time a boat drops anchor in the sea grass it damages the grass, breaks off pieces, and then it spreads and starts to grown new colonies.

Native sea grasses buffer currents, surge, and reduce beach erosion.

"The four species we have here do a good job of maintaining sediment," Forbes said. "But we don't know if this does the same thing."

Controlling sediment is critical because too much sediment - dirt and particles - can smother corals and lead to the decline of the healthy reef environment. It also keeps the water clear, which is better for snorkeling and diving, two activities that are very important to the territory's tourism industry.

The native sea grasses that are most abundant are the Syringodium filiforme, Thalassia testudinum and Halodule wrightii.

"Faculty and students at UVI are meeting this threat to our native marine communities with the full-force of research, knowledge and education," Forbes said.

UVI Marine and Environmental Sciences graduate students Sam Mitchell and Jess Keller recently wrapped up a study of the invasive sea grass as a part of the capstone project for their degrees. Their study revealed evidence that local animals eat the invasive sea grass, but the rate of consumption is not sufficient to prevent its expansion, according to UVI.

"This may have dire consequences for shallow, tropical marine ecosystems, since many organisms rely on native sea grasses for food and shelter," Mitchell said in a written statement.

The university's staff and students will continue to study this rapidly spreading grass to track its impact on the local marine environment, Forbes said.

"There's an assortment of different research projects going on with Halophila right now," Forbes said.

He said studies are on going that are looking at the distribution of the grass around the territorial waters.

"There's talk of doing some work on nutritional analysis of the Halophila and a more in-depth look at what species might eat the Halophila," Forbes said.

Researchers are asking the public to help out by calling in to report sightings of the invasive grass, so they can keep tracking its spread.

"It would be good if people report where they see it," Forbes said.

Halophila stipulacea is commonly found in disturbed at a depth of 98 to feet. Its leaves are usually no bigger than about a half inch long.

"An awareness campaign will target mitigation measures to prevent further expansion and any future invasions of non-native species," Keller said in a written statement. "Careful control of invasion vectors such as boat ballast storage areas, mobile attachments and the hulls of boats is necessary."

Boaters are asked to avoid anchoring in sea grasses. This will limit damage to native sea grasses and discourage the growth of non-native sea grasses.

To report sightings of Halophila stipulacea to the UVI Center of Marine and Environmental Science call 693-1672.