RESUMEN
The ratio of stable carbon isotopes (δ13C) in plants and animals from Malaysian mangrove swamps, coastal inlets, and offshore waters was determined. Vascular plants of the swamps were isotopically distinct ( x±s.d.=-27.1±1.2) from plankton (-21.0±0.3) and other algae (-18.7±2.2). Animals from the swamps (-20.9±4.1) and inlets (-19.8±2.5) had a wide range of isotope ratios (-28.6 to-15.4), indicating consumption of both mangrove and algal carbon. Several commercially important species of bivalves, shrimp, crabs, and fish obtained carbon from mangrove trees. Mangrove carbon was carried offshore as detritus and was isotopically distinguishable in suspended particulate matter and sediments. Animals collected from 2 to 18 km offshore, however, showed no isotopic evidence of mangrove carbon assimilation, with ratios (-16.5±1.1, range-19.1 to-13.1) virtually identical to those reported for similar animals from other plankton-based ecosystems. Within groups of animals, isotope ratios reflected intergencric and interspecific differences in feeding and trophic position. In particular, there was a trend to less negative ratios with increasing trophic level.
RESUMEN
The 13C/12C ratios in orange juice are sufficiently uniform and different from those in high fructose corn syrup (HFCS) so that the addition of HFCS to orange juice can be detected. HFCS averages -9.7% (parts per thousand) delta 13C, orange juice averages -24.5%, and mixtures of HFCS and orange juice possess intermediate values. One pure orange juice and 4 orange juice -HFCS mixtures containing from 25 to 70% orange juice were properly classified by 7 collaborators. Samples with delta 13C values less negative than -22.1%, 4 standard deviations from the mean of pure juices, can, with a high degree of confidence, be classified as adulterated. Samples with values more negative than -22.1% must be considered unadulterated with HFCS, because pure orange juices possess a range of delta 13C values. The 13C/12C mass spectrometric method was adopted official first action for detecting HFCS in orange juice.
