University of the Virgin Islands faculty and student researchers are assessing the presence and spread of Halophila stipulacea, an invasive species of sea grass that is quickly spreading throughout the territory’s waters. Halophila stipulacea originates from the western Indian Ocean and is thought to have spread into the Mediterranean and Caribbean seas in ship ballasts and by fragmentation caused by anchoring and other bottom disturbances.
“Controlling the spread of this invasive species is critical due to its high capacity to replace and displace existing, native sea grass beds,” said Howard Forbes Jr., UVI Virgin Islands Marine and Advisory Service coordinator. “We are not sure what consumes this sea grass and so should it completely dominate the marine ecosystem, it could mean the loss of food and habitat for some ecologically important marine organisms.”
“Faculty and students at UVI are meeting this threat to our native marine communities with the full-force of research, knowledge and education,” he said.
UVI Marine and Environmental Sciences graduate students Sam Mitchell and Jess Keller are a part of UVI’s Masters in Marine and Environmental Science 2013 cohort who 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.
The native sea grasses that are most abundant are the Syringodium filiforme, Thalassia testudinum, and Halodule wrightii. These native sea grasses are threatened by the invading sea grasses, as they compete for resources and space. The invasive sea grass’ fast growth rate and its ability to regenerate from a tiny fragment enables it to rapidly establish new colonies in bare sand. This may have dire consequences for shallow, tropical marine ecosystems, since many organisms rely on native sea grasses for food and shelter,” said Mitchell, a UVI graduate student. Also, sea grasses buffer currents, surge, and beach erosion.
Mitchell said another concern is that the invasive species has been observed to grow in the sand halo that typically surrounds coral reefs. This is important because this is an area where sea grasses are absent and represents an ideal location for the invasive species of sea grass to take root.
UVI needs the public to report any sightings of the invasive sea grass, especially if it appears in any of these native sea grass habitats. Halophila stipulacea is commonly found in disturbed areas of between 98-147 feet in depth. Its leaves are usually between .11 to .59 inches long and .11 to .38 inches wide, which is small in comparison to the native species of sea grasses found within the Caribbean. “An awareness campaign will target mitigation measures to prevent further expansion and any future invasions of non-native species,” said Keller, a UVI graduate student. It is also important to identifying bays and estuaries that have not yet been invaded. “These native strongholds are precious commodities at risk of invasion that need protection from the non-native species,” she said. “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 encourage the growth of non-native sea grasses.
Anyone with knowledge of the presence of the foreign sea grass Halophila stipulacea, please report the sighting to the UVI Center of Marine and Environmental Science at (340) 693-1380.