Upper trophic structure in the Atlantic Patagonian shelf break as inferred from stable isotope analysis
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The Patagonian Shelf is a very productive region with different ecosystem structures. A long history of fishing in the Southwestern Atlantic Ocean combined with a complex hydrographic structure, with a permanent front over the shelf-break and different coastal frontal regions, and a wide non-frontal area in between have made the food web in this area more complex and have resulted in changes to the spatialtemporal scale. Stable isotopes of carbon and nitrogen were used to determine the trophic structure of the Patagonian shelf break which was previously poorly understood. The results indicated that the average δ15N value of pelagic guild (Illex argentinus) was remarkable lower than those of the other guilds. The δ13C values of almost all species ranged from -17‰ to -18‰, but Stromateus brasiliensis had a significant lower δ13C value. Compared with the southern Patagonian shelf, short food chain length also occurred. The impact of complex oceanographic structures has resulted in food web structure change to the temporal-spatial scale on the Patagonian shelf. The Patagonian shelf break can be considered as a separated ecosystem structure with lower δ13C values.
Keyword13C 15N trophic structure Patagonian shelf break
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We would like to thank the fisheries observers, crew and the officers of the trawler Longfa, LIU Zijun, CHEN Lvfen, WANG Rui, SONG Qi and REN Zeqian at the College of Marine Sciences, Shanghai Ocean University for their helps in processing the samples. We acknowledge Mr Alan Coughtrey of the Shanghai Ocean University for his help in polishing the language. Finally, we would also like to thank two anonymous reviewers for their contributions to improve this manuscript.
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