δ 13C of zooplankton, decapod crustaceans and amphipods from Laguna de Terminos, Campeche (Mexico), with reference to food sources and trophic position

Abstract

Zooplankton, Penaeus setiferus, P. duorarum, Xiphopenaeus kroyeti, Callinectes sapidus, Dyspanopeus texanus, Palaemonetes spp., Hippolyte spp. and amphipods were isotopically characterized to identify the food sources they use and their relative trophic position, as well as to establish a relationship between the isotopic data and the isotopic “memory”, the isotopic convergence and the complexity of trophic chains. The δ ¹³C values of the animals were compared to those of the submerged vegetation, detritus and sediment of each locality. The range of δ ¹³C values of –7.2 to –24‰ indicates that consumers take advantage of sources of organic carbon of a diverse isotopic nature. The isotopic difference between the lager consumers, P. setiferus, P. duorarum, X. kroyeri, C. sapidus and D. texanus, and the primary producers indicates that the first occupy a high trophic level within their communities. There is a relationship between the migration of P. setiferus juveniles from the northeast (CTL = 11.5 mm) to the southwest (CTL = 22.5 mm) of the lagoon, and the variation in isotopic composition from heavier (–8.9‰) to lighter (–24.2‰) δ ¹³C values. Three cases are presented to explain the variety of δ ¹³C values of P. setiferus. In general, the isotopic composition of the above-mentioned species characterized two isotopically different areas: one to the northeast of the system with heavier values of –6.4 to –17.2‰ and another to the west, southwest and South with lighter values of –15.3 to –24.2‰.