In order to understand the characteristics of food web structure in Zhongjieshan Islands, consumer samples of fish, shrimp and crabs, cephalopods, shellfish and zooplankton were collected from Zhongjieshan Islands in July 2020. Based on the carbon and nitrogen stable isotope techniques, the contributions of the four potential carbon sources (macroalgae, phytoplankton, suspended particulate organic matter (POM) and substrate organic matter (SOM)) to consumers, as well as the food web structure and nutritional relationship of the Zhongjieshan Islands were analyzed. The results revealed that the δ13C values of carbon sources ranged from −22.93‰ to −9.73‰, and the δ15N values ranged from 1.72‰ to 7.68‰. The δ13C values of consumers ranged from −21.95‰ to −12.55‰, and the δ15N values of consumers ranged from 4.13‰ to 12.92‰. One-way analysis of variance showed that there were significant differences in carbon and nitrogen stable isotopes among different carbon sources and different groups of consumers (p<0.01). SIBER model was used to analyze the trophic structure indexes of the regional ecosystem of Zhongjieshan Islands. Compared with the research results of other sea areas, it was found that the level of food source diversity (CR), trophic level length (NR) and total niche area (TA) were relatively high. SIAR model was used to calculate the carbon source contribution rate. The results showed that phytoplankton and POM were important carbon sources, with an average contribution rate of 29.63% and 28.72%. The maximum contribution rate of phytoplankton to zooplankton was 80.58%, and the maximum contribution rate of POM to fish was 79.74%; the maximum contribution rate of SOM to shrimp and crab was 49.94%; the carbon source contribution of macroalgae to consumers was the lowest, with an average of 18.37%. The mean trophic level range of the main consumers in Zhongjieshan Islands was 1.58 to 3.63, and the trophic level was 3. The average trophic level from big to small was as follows of cephalopods (3.09), fish (3.00), shrimps and crabs (2.70), shellfish (1.82). The consumers in the waters of Zhongjieshan Islands were mainly low and intermediate carnivores, and there were few omnivores and high carnivores. This study initially constructed the ecosystem food web of Zhongjieshan Islands, which provided reference data for understanding the trophic structure in this area, and also provided theoretical information for further study of the ecosystem.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |