Food web structure and trophic levels in a saltwater pond sea cucumber and prawn polyculture system
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Food web structure and trophic levels in a saltwater pond sea cucumber and prawn polyculture system GUO Kai1, ZHAO Wen1*, WANG Shan1, LIU Baozhan2, ZHANG Peng1 1 Key Laboratory of Hydrobiology in Liaoning Province, Dalian Ocean University, Dalian 116023, China 2 Offshore Environment Services Co., Ltd., Tianjin 300452, China
Received 9 October 2014; accepted 31 July 2015 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2016
Abstract
The food sources of aquacultured Apostichopus japonicus and the trophic levels of organisms in a sea cucumber (A. japonicus) and prawn (Penaeus japonica) polyculture system in a saltwater pond in Zhuanghe, Liaoning Province were examined using carbon and nitrogen stable isotopes. Across organisms, δ 13 C ranged from (–25.47±0.20)‰ to (–16.48±0.17)‰ (mean±SD), and δ15N ranged from (4.23±0.49)‰ to (12.44±0.09)‰. The δ13C and δ15N contents of A. japonicus, P. japonica and Fenneropenaeus chinensis were comparatively higher than those of other organisms. Values of δ13C and δ15N revealed that P. japonica, Hemigrapsus sanguineus and Neomysis japonica comprised the largest component of the diet of A. japonicus. The mean trophic level of the organisms in this saltwater pond polyculture system was (2.75±0.08). P. japonica, A. japonicus, F. chinensis, Synechogobius hasta and Neomysis japonica were in the 3rd trophic level (2–3); jellyfish, H. sanguineus and zooplankton were in the 2nd trophic level (1–2); and Enteromorpha prolifera, benthic microalgae, periphyton and suspended matter primarily consisting of phytoplankton, bacteria and humus were in the primary trophic level (0–1). Key words: Aposticbopus japonicas, Penaeus japonica, stable isotopes, food web structure, diet composition, trophic level Citation: Guo Kai, Zhao Wen, Wang Shan, Liu Baozhan, Zhang Peng. 2016. Food web structure and trophic levels in a saltwater pond sea cucumber and prawn polyculture system. Acta Oceanologica Sinica, 35(4): 58–62, doi: 10.1007/s13131-016-0834-9
1 Introduction The sea cucumber Apostichopus japonicus (Selenka) is an echinoderm (Holothuroidea, Aspidochirotida, Apostichopus) found only in the northern coastal waters of China (Liaoning, Shandong and Hebei Provinces). Because of its high nutritional value and medicinal applications, A. japonicus has become an important aquaculture species with over 170 000 tons production in China (Fisheries Department of Agriculture Ministry of China, 2013), over 64 500 tons of which is produced in the main culture area of Liaoning Province. Pond-cultured A. japonicus are not generally fed artificial diets in China, as natural food sources in the pond waters are sufficient. Studies have shown that polyculture ponds have higher nutrient use efficiency than monoculture ponds (Wang and Qi, 1998), and integrated culture of sea cucumbers with other aquatic organisms can improve resource utilization and production (Ahlgren, 1998; Kang et al., 2003; Slater and Carton, 2007; Paltzat et al., 2008). The culturing of sea cucumbers with prawns is a common pol
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