Chelonia mydas (Green Sea Turtle) forage at Higher Rates on Native Caribbean Seagrasses Despite Higher Coverage of Non-native Halophila stipulacea

Since 2002, the non-native seagrass Halophila stipulacea has spread throughout subtidal habitats in the Caribbean. The ecological effects of the seagrass are still poorly understood, and the impacts of this invasion on the ecology of endangered Chelonia mydas (Green Sea Turtle), which graze on native Caribbean seagrasses, are of special concern. We conducted short-term (30-min) observational surveys of the feeding behavior of 20 individual turtles within 3 bays in St. John, US Virgin Islands that had mixed assemblages of native and invasive seagrasses, and recorded bites taken by turtles on each seagrass type. We found that while turtles consumed H. stipulacea, they disproportionately foraged on native seagrass species (99.98% of bites). For example, though average cover was higher for H. stipulacea than for native seagrasses, C. mydas consumption of native seagrasses was 53-times higher than of the non-native species. These patterns suggest that, at least for the present time, C. mydas in St. John prefer native seagrasses over H. stipulacea. Whether these feeding patterns impact plant community structure should be further investigated experimentally.