Video

A presentation at the 2007 Hawai`i Conservation Conference by Karla J. McDermid1, (and George H. Balazs2, 1University of Hawai‘i at Hilo, Hilo, HI, 2NOAA-National Marine Fisheries Service, Honolulu, HI) on "Making a Living on Limu: Nutritional Composition of Marine Plants in the Diet of the Green Sea Turtle (Chelonia mydas) in the Hawaiian Islands". Over 275 seaweeds and two seagrasses are eaten by Hawaiian green turtles, Chelonia mydas Linnaeus, the most common sea turtle and the largest marine herbivore in the Hawaiian Islands. The Hawaiian green turtle population has increased in numbers since protection under the U.S. Endangered Species Act; however, there has been a long-term decline in immature turtles’ somatic growth rates. Because forage type and nutrition may have a role in green turtle growth, reproduction and long-term species viability, 16 macroalgal species, two seagrass species, and multi-specific turf from turtle foraging areas on four different islands were analyzed for protein, lipid, carbohydrate, water, ash, energy, amino acid, vitamin and mineral content. A rhodophyte, Pterocladiella capillacea (Gmelin) Santelices & Hommersand, a prominent dietary item, and a chlorophyte, Rhizoclonium implexum (Dillwyn) Kützing, an infrequently consumed species, ranked highest in total protein content. Most species contained <10% crude lipid. Soluble carbohydrates ranged from 3.2-39.9 % dry weight. Ash values ranged from 13.7-81.4% dry weight. Energy content of Pterocladiella capillacea was >14 kJ g-1 ash-free dry weight. All species tested contained measurable quantities of 11 minerals. Vitamin A was detected in all marine plants tested; most contained Niacin; and Enteromorpha flexuosa (Wulfen) J.Agardh, a chlorophyte, had the highest amount of Vitamin C (3 mg g-1). Samples contained measurable amounts of all essential amino acids, except tryptophan. These data provide new information about Hawaiian green turtle feeding ecology, and factors that may influence somatic growth rate.