Trophic structure of macrobenthos in artificial reef area of Furong Island, Laizhou Bay

Artificial reef is an effective measure for improving benthic habitat, macrobenthos diversity, and richness. Its ecological effects are closely related to the duration of placement. In order to explore the effect of reef construction duration on the trophic relationship of macrobenthos, this study applied stable isotope techniques to compare the carbon and nitrogen stable isotope compositions of macrobenthos and their food sources in artificial reef areas of different ages and control areas in the coastal waters of Furong Island, Laizhou. In addition, the food bases and trophic levels of macrobenthos in different areas were also calculated. The results showed that: ① The δ¹³C values of macrobenthos in long-age reef area, short-age reef area and control area ranged from −25.08‰-−13.34‰, −25.86‰-−17.80‰, and −25.39‰-−11.06‰, respectively. The corresponded δ¹⁵N values ranged from 10.73‰-15.78‰, 10.02‰-14.89‰, and 10.17‰-15.80‰, respectively. ② Compared to short-age reef and control area, the macrobenthos community in the long-age reef area has higher trophic diversity, higher diversity of food sources, more diverse trophic niches within the community and better stability of community structure. ③ According to feeding habits, macrobenthos can be divided into four functional groups, namely planktonophagous group (Pl), carnivorous group (C), detritivorous group (D) and omnivorous group (O). Among the four potential food sources (phytoplankton, zooplankton, particulate organic matter (POM) and sediment organic matter (SOM)), phytoplankton had the highest average contribution (31.40%) to the three types of consumers, except for carnivorous group. ④ The trophic levels of consumers in long-age reef , short-age reef , and control area were 2.00–3.83, 2.00–3.49 and 2.00–3.87, respectively. In addition, higher trophic level predators were observed in long-age reef area, implying more complex trophic structure in long-age reef area than that of other areas. The results of this study showed that the construction of artificial reefs could enhance the utilization of carbon sources of phytoplankton by macrobenthos, increase the trophic diversity and richness of macrobenthos community, and increase the numbers of higher trophic animals in the community. The results of this study contribute to the existing knowledge for understanding the ecological effects of artificial reef construction and provide basic information for further studies on the material cycle and energy flow of benthic food web.