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Medientyp:
E-Artikel
Titel:
Stable Isotope Discrimination by Consumers in a Tropical Mangrove Food Web: How Important Are Variations in C/N Ratio?
Beteiligte:
Schwamborn, Ralf;
Giarrizzo, Tommaso
Erschienen:
Springer Science+Business Media, 2015
Erschienen in:Estuaries and Coasts
Sprache:
Englisch
ISSN:
1559-2723;
1559-2731
Entstehung:
Anmerkungen:
Beschreibung:
<p>Stable isotopes are widely used as tracers in food webs and as indicators of the trophic levels (TL) of consumers. The objectives of this study were to verify a possible ecosystem-wide increase in the relative contribution of the heavy isotope with trophic level, for carbon and nitrogen, and to analyze the relationships of C/N ratios and stable isotope ratios of consumers in a tropical mangrove food web. Samples of primary producers and consumers (benthic invertebrates, zooplankton, 31 fish species, and other vertebrates) were collected in the Curuçá Estuary, northern Brazil. Our results showed that the relative amount of the heavy isotope significantly increased with TL. Linear models of δ¹⁵N vs TL were highly significant and explained 75 % of the total variability in food web δ¹⁵N. Models for δ¹⁵N yielded a much better fit than the models built for δ¹³C, mainly due to a higher variability in source δ¹³C and stronger trophic discrimination for ¹⁵N than for ¹³C. Enrichment in δ¹⁵N was 2.3±0.20% per TL (all data). The increase in δ¹³C with TL, in spite of being significant, could not be used to estimate trophic enrichment, since it was affected by the concentration of predatory fish in a ¹³C-rich algae-based food web. Furthermore, the increase in δ¹³ C with TL could be fully explained by the change in C/N ratio (i.e., lipid content) with TL. Our results demonstrate the importance of considering TL and C/N ratios in stable isotope analyses of food webs.</p>