Two lines of evidence indicate green sea turtle Chelonia mydas grazes the aggressive macroalga Chondria tumulosa at Midway Atoll (Kuaihelani), Papahānaumokuākea Marine National Monument
摘要
Underwater video recordings and a necropsy of a recently dead adult female confirm that the green turtle, Chelonia mydas, readily grazes the aggressive red alga Chondria tumulosa. Present in Papahānaumokuākea Marine National Monument since 2016, C. tumulosa has demonstrated the capacity to aggressively overgrow live coral and successfully attach to calcareous reef substrate. A stationary GoPro Hero camera captured ~ 50 min of a group of three grazing turtles with one exhibiting a burst of up to 18 bites of C. tumulosa, in a 95-s interval. Fragments of C. tumulosa were identified in the esophagus, crop, and in the feces of the necropsied female. In the freshly consumed food matter, C. tumulosa visually appeared to represent approximately 25% of plant material and was the same color as the upper canopy tissues we observed during grazing in the reef videos. The video evidence demonstrates that this native megaherbivore has the potential to remove substantial C. tumulosa biomass and highlights a likely positive role for C. mydas in the control of C. tumulosa. The necropsy also highlights the potential negative effect C. mydas may have in the inadvertent spread and distribution of C. tumulosa, adding urgency to our need to learn more about these important species interactions.