Nutritional composition of marine plants in the diet of the green sea turtle (Chelonia mydas) in the Hawaiian Islands

In the Hawaiian Islands, seaweeds and seagrasses are eaten by green turtles, Chelonia mydas Linnaeus. Sixteen macroalgal species (7 Chlorophyta, 2 Phaeophyta, 7 Rhodophyta), two seagrass species, and multi-specific algal turf from turtle foraging areas on four different islands were analyzed for proximate (protein, lipid, carbohydrate), water, ash, energy, amino acid, vitamin, and mineral content. Pterocladiella capillacea (Gmelin) Santelices and Hommersand, a prominent dietary item, and 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 P. capillacea was over 14 kJ g–1 ash-free dry weight. All species tested contained measurable quantities of 11 minerals. Vitamin A (β-carotene) was detected in all marine plants tested; most contained Niacin (B3 ); and Enteromorpha flexuosa (Wulfen) J. Agardh had the highest amount of vitamin C (3 mg g–1). Samples contained measurable amounts of all essential amino acids, except for tryptophan. These data provide new information about Hawaiian green turtle feeding ecology and factors that may influence somatic growth rates.