Halophila stipulacea, a potentially invasive sea grass, was found in the waters around St. Thomas and St. John in 2014 but, until this week, its presence has not been confirmed on St. Croix.
The species originated in the Red Sea and Indian Ocean and is thought to have spread into the Mediterranean and Caribbean Seas in ships’ holds and ballast water or fragmentation caused by anchoring and other bottom disturbances. Currently H stipulacea is present from the U.S. and British Virgin Islands south to Grenada.
University of the Virgin Islands researcher Marcia Taylor found and identified a fragment of H. stipulacea this week while walking on the beach west of Christiansted Harbor looking for marine samples for her class.
Taylor said the segment of sea grass may have drifted here and was definitely alive and growing. Usually it is found on the sea floor but this sample was floating on the surface with other sea grass, she said.
“It’s just now, as of this week, seen on St. Croix,” Taylor said. “ We knew that the species would appear on St. Croix eventually but we were not looking forward to it.”
Although H. stipulacea has been studied by the Virgin Islands Experimental Program to Stimulate Competitive Research on St. Thomas, no determination has been made whether it is harmful to other sea plants and marine life.
It grows quickly and competes with other species for space, which “may or may not be a bad thing,” Taylor said.
Unlike seaweed and sargassum, which are algae, H. stipulacea is a true flowering plant that grows in shallow mud and sand to depths of 100 feet.
According to Taylor, if the sea grass chokes out other species that turtles and fish eat, it may disrupt their habits and cause them to move to other locations.
Another potential problem, Taylor said, is that the new species is not as stable and is easily uprooted. After a storm, beaches could become littered with quantities of decaying H. stipulacea.
More research of the underwater areas around the island is needed, Taylor said. She hopes that residents will contact her at mtaylor.uvi.edu or UVI if they come across samples of the sea grass. Findings can also be reported to invasiveseagrass.org.
According to the invasive sea grass website, leaves are usually between 1 and 3 inches long and a half-inch wide. The blades are oblong and the tip is serrated and found in clusters of two to six blades growing together from a single shoot in the sand. The shoots are linked by a horizontal root structure or rhizome.