Nutrient Input from Green Turtle Eggs and Hatchlings in a West Africa Island and Its Nearshore Environment

Abstract Sea turtle nesting brings marine-derived nutrients into sandy beach ecosystems, potentially influencing their dynamics. We investigated nutrient input from green turtle Chelonia mydas eggs and hatchlings into coastal habitats in Guinea-Bissau, West Africa. We assessed two islands within the João Vieira-Poilão Marine National Park (‘JVPMNP’), with contrasting sea turtle nesting density: very low (João Vieira) and very high (Poilão). On each island, we analyzed stable isotopes of carbon and nitrogen in one pair of plant species (coinvine Dalbergia ecastaphyllum bush/baobab Adansonia digitata tree) and two pairs of predator species (tufted ghost crab Ocypode cursor /African rainbow crab Cardisoma armatum and sea catfish Carlarius spp./crevalle jack Caranx hippos ). The first species in each pair is distributed closer to nesting sites, while the second is found further inland or offshore. Stomach content analysis was also conducted for fishes. Results supported nutrient input from turtle clutches benefiting the species living near nesting sites. Shoreline coinvines at Poilão had higher δ 15 N (5.1 ± 3.2‰) compared to João Vieira (≈0‰), suggesting assimilation of turtle-derived 15 N. Shoreline tufted ghost crabs at Poilão had enriched δ 15 N (15.2 ± 0.7‰ vs. João Vieira’s 12.2 ± 1.1‰) and δ 13 C (− 13.4 ± 0.7‰ vs. João Vieira’s − 18.7 ± 1.4‰), likely reflecting predation upon eggs and hatchlings. Sea catfishes at Poilão frequently consumed unhatched turtle eggs washed into the sea (17% frequency of occurrence) and hatchlings (up to 27%). This study suggests that nutrient availability from turtle nests influences and supports shoreline plants and consumers at JVPMNP.