Use of isotopic signatures to assess the food web in a tropical shallow marine ecosystem of Southeastern Brazil

Abstract

A dual isotope approach was used to assess the relative importance of terrestrial vegetation detritus and other primary producers in the trophic web of Flamengo Sound (Ubatuba, SP), SE Brazil, surrounded by the Atlantic Rain Forest. Primary producers showed distinct d 13 C signatures and the observed values suggest that little terrestrial ðÀ29:4 AE 0:3‰Þ or bulk sediment organic matter ðÀ21:1 AE 1:3‰Þ enter the food web of the sound. Suspended particulate organic matter (POM, À18:6 AE 0:5‰Þ supports the bulk of the consumers, with some contribution by macroalgae ðÀ15:6 AE 1:8‰Þ. Consumers d 13 C values ranged from )17.4 to À12:7‰. At least three trophic levels were detectable in the food web. The d 15 N value of POM was 7:5 AE 1:0‰, while that of sediment and detritus was 6:4 AE 0:7‰. The d 15 N values of suspension feeding benthic invertebrates were 8.2-8:6‰, deposit feeders 8.3-10:2‰, and carnivores 10.7-13:2‰. Values for fishes were 9:4‰ for detritivore, 11.4-13:3‰ for benthic feeders, 12.4-13:3‰ for zooplanktivores, and 13:2‰ for piscivores/benthic invertebrate feeders. Squid mean value was 12:8 AE 0:5‰. There is a reasonable agreement between feeding habits information from the literature and d 15 N values from this study. In the sound, the first and second trophic steps seem to be about 1-3‰ higher than those of similar organisms studied in temperate waters and this may reflect an input of allochtonous anthropogenic nitrogen enriched in 15 N from human activities.

Mercury and stable isotopes (δ15N and δ13C) as tracers during the ontogeny of Trichiurus lepturus

“…Kidd et al, 1995;Corbisier et al, 2006;Al-Reasi et al, 2007;Faye et al, 2011). In general, stable isotope ratios of a predator are related to the isotopic composition of their prey.…”

Differences in the feeding of Rhamdia quelen (Siluriformes, Heptapteridae) in four distinct lotic systems

“…Some food items have been abundant in all the analyzed systems, and insects during their immature stages (Chironomidae larvae and pupae) use to be the main consumed invertebrate and are in some way also dependent on the external resources (Alvin and Peret, 2004). An important parameter of the external (terrestrial) influence to maintain the fish an general water community may be represented by the continuous entrance of the organic matter to the aquatic system, in a clear difference to what happens to the sea (Corbisier et al, 2006), as a food resource to the autochthonous organism living in the rivers, as the aquatic insects also depend on the flooding situations when such resources are incorporated to the aquatic medium. (Walker et al, 1990).…”

Trophic structure of benthic communities in the Cabo Frio upwelling system (southeastern Brazilian shelf): a temporal study using stable isotope analysis

“…SI ratios are conventionally presented as the deviation from a standard material in parts per thousand (‰), as follows: δ Each species/family of macrofauna and megafauna was assigned to one of the following functional feeding groups: suspension feeder, surface deposit feeder, subsurface deposit feeder, omnivore, or carnivore and/or scavenger (references in Corbisier 2006). The functional feeding groups of close taxonomical groups were used when no information was available.…”

“…Studies in tropical marine shelf systems have mainly been conducted nearshore on hard substrates or coral reefs (revision in Mallela & Harrod 2008). In SE Brazil off Ubatuba, a subtropical region, only the marine coastal area was evaluated (Matsuura & Wada 1994, Corbisier et al 2006.…”