Nonnative Seashore Paspalum, Paspalum vaginatum (Poaceae), Consumed by Hawaiian Green Sea Turtles (Chelonia mydas): Evidence for Nutritional Benefits

The Hawaiian green turtle, Chelonia mydas Linnaeus, is a marine herbivore known to feed on sea grasses and seaweeds. On the east side of the island of Hawai‘i, at high tide, green turtles have been observed feeding on a terrestrial, salt-tolerant turfgrass: seashore paspalum, Paspalum vaginatum Swartz, first introduced to the Hawaiian Islands in the 1930s. The role of this grass in green turtle nutrition is unknown. Paspalum vaginatum samples were collected at Keaukaha Beach Park, Hilo, and analyzed for nutritional composition (percentage water, percentage ash, caloric value, C:N ratio, percentage protein, and percentage lignin). In addition, two red seaweeds, Pterocladiella capillacea (Gmelin) Santelices & Hommersand, a common food source for green turtles, and Ahnfeltiopsis concinna (J. Agardh) Silva & DeCew, an abundant high-intertidal species sometimes consumed by turtles, were analyzed for comparison. In contrast to the two seaweed species, Paspalum vaginatum contained approximately half the ash; 300–1,500 more calories/g ash-free dry weight; three to four times greater total protein; and 3–19 times higher lignin content. Green turtles in Hawai‘i may opportunistically consume P. vaginatum because of its local abundance and/or its high protein and caloric content. In foraging areas where native macroalgal species have declined and/or turtle carrying capacity has been reached, green turtles may exploit new foods, such as seashore paspalum, and perhaps mitigate decline in somatic growth rates and body condition.