Abstract: Beach debris at spawning grounds is a major threat to the nesting and hatching of sea turtle. The Qilianyu Islands, a subgroup of islands in the northeastern part of the Xisha Islands, is the largest spawning ground for green sea turtles (Chelonia mydas) in China. Although this site is far from the mainland and relatively isolated with a small human population, pollution could not be ignored. We surveyed beach debris in and around the spawning ground of C. mydas on six islands of Qilianyu. We found that the beach debris consisted of plastic, metals and glass, with plastic being the dominant type, accounting for 82.07% in number and 45.98% in mass. The average number density of beach debris was 0.38 pieces·m^-2, and the average mass density was 7.66 g·m^-2. Compared with other spawning grounds, the average density of beach debris here was lower, but with higher proportion of plastic debris. After categorizing the type of debris, we found that most debris was from household goods (74.33%), followed by that from shipping/fishing activities (9.11%). Based on the words on the plastic debris, we inferred that the geographic source was primarily from abroad (82.02%), mainly from Southeast Asian countries, such as Vietnam and Malaysia, accounting for 96.3% of foreign debris. To better protect this important spawning ground, we recommend strengthening beach debris reduction and cleanup at Qilianyu, with much stronger regional cooperation.

Key words: fuel., drying coefficient, wind speed, moisture content