Food web foundation and seasonal variation of trophic structure based on the stable isotopic technique in the marine ranching of Haizhou Bay, China

Abstract

Stable isotope technique was applied to investigate the small and medium-size consumers including not only fish, shrimps, crabs, cephalopods, snails and bivalves, but also the specimens of their potential carbon sources, which were collected in the marine ranching area of Haizhou Bay during the spring of 2015. IsoSource model was adopted to calculate the contribution of potential carbon sources to the consumers. Biospeciemens collected in the summer of 2014 were compared with those in the spring of 2015, aiming to analyze the seasonal variation in the trophic structure of food web. Six quantitative community indices were calculated based on the isotope values of the organisms in Haizhou Bay. The results showed that the δ13C values of consumers ranged from -18.9‰ to -17.1‰, and the δ13C values of three potential food sources ranged from -18.1‰ to -23.4‰ in the spring of 2015. The calculation results of IsoSource model further demonstrated that the phytoplankton was the most important carbon source for consumers (80.8%), followed by sediment organic matter (10.8%) and particulate organic matter (8.4%). There was a significant difference in the δ13C values between the biospecimens in the summer of 2014 and those in the spring of 2015, while no significant difference was observed in δ15N values. Trophic structure of community-wide differed remarkably in different seasons indicated by the six quantitative community indices. The δ13C range, total area, mean nearest neighbor distance and standard deviation of nearest neighbor distance of the community were much higher in 2014 than those in 2015, but the δ15N range and mean distance to centroid showed no significant change. The trophic structure redundancy was lower in the summer of 2014 compared with that in the spring of 2015, however, the diversity of food resources was higher in the summer of 2014.