Discipline: Ecology Environmental and Earth Sciences
Kyle Jerris - University of the Virgin Islands
Co-Author(s): Teresa Turner, University of the Virgin Islands, USVI
The West Indian Sea Egg (Tripneustes ventricosus) is one of the most prominent grazers on Caribbean seagrass beds. On some Caribbean islands such Martinique and St. Lucia, there is a commercial fishery for it. Because Caribbean seagrass beds are being invaded by the Indian Ocean seagrass Halophila stipulacea, T. ventricosus is a prime candidate to control it. This study conducted on St. Thomas United States Virgin Islands, aimed to determine whether Tripneustes can act as a biological control for Halophila as well as what effects this seagrass might have on the urchin. To determine site preference, surveys were conducted at three habitat types. These surveys showed that theses urchins preferred turtle grass (Thalassia testudinum) beds and rock substrate over Halophila beds (ANOVA p=0.0022). Only one urchin was found in a Halophila bed, suggesting it might not control the invasive seagrass. A multi choice feeding experiment was then conducted to determine preference among the seagrass species found on the island. The experiment showed that T. ventricosus greatly preferred T. testudinum over any of the other seagrasses. (Friedman test p=0.0001) To further determine if the West Indian Sea egg would be a suitable biocontrol for H. stipulacea, urchins were fed either Halophila or Thalassia for five weeks. At first some of the urchins in the Halophila treatment refused to eat. After some time, more urchins started to eat the Halophila, which suggests that they can eat Halophila in natural conditions. As a proxy for health, I observed the urchins’ righting behavior. The majority of the Halophila treatment urchins had a dropping behavior when righting themselves, suggesting that they have poor health on this food. Thus Tripneustes probably cannot control Halophila and indeed its population might be negatively impacted by the invasion.
Funder Acknowledgement(s): This research was supported in part by the National Science Foundation’s Virgin Islands Experimental Program to Stimulate Competitive Research (VIEPSCoR award #1355437) and the Center for Marine and Environmental Studies at the University of the Virgin Islands.
Faculty Advisor: Teresa Turner,