STABLE ISOTOPIC STUDIES ON CHITIN (ARTHROPODS, CRUSTACEANS, ECOLOGY, CHEMICAL ARCHAEOLOGY, CLIMATOLOGY)

Carbon, nitrogen, oxygen, and hydrogen stable isotope ratios of the poly-amino-sugar chitin isolated from exo-skeletons of 75 arthropod species collected in 59 locations were determined. The objectives were to understand the environmental, climatic, and biological influences on the isotope ratios and to develop a data base for interpreting isotope ratios of archaeological and fossil chitins. Measurements of stable isotope ratios in chitin isolates showed large variations which reflect intrinsic compositional and isotopic heterogeneities as well as differences caused by methods of preparation. Analyses of D-glucosamine hydrochloride for determinations of ('13)C/('12)C, ('15)N/('14)N, and ('18)O/('16)O ratios (the latter by a new analytical method described herein), and of chitose dehydration products for D/H ratios of carbon-bound hydrogen, eliminated these problems as well as the influence of exchangeable hydrogen. No biochemically derived isotopic differences were found between chitins from Insecta, Crustacea and Merostomata. The infraindividual isotopic variability in a lobster and isotopic differences among sexes and old and new carapaces sampled along crustacean molting were small, non-systematic, and similar to interindividual variabilities within crustacean populations. Age was no source of variance if growth was not accompanied by shifts in diet or habitat. Marine (delta)('13)C values averaged 9.1 ('o)/oo less negative than terrestrial ones, allowing for detection of local terrigeneous pollution in coastal ecosystems. (delta)('13)C values tended to become more negative towards higher latitude. (delta)('15)N and (delta)D values reflected trophic levels, while displaying large variations among different ecosystems. Terrestrial (delta)D and (delta)('18)O values were generally more negative than marine ones. (delta)D values were largely influenced by those of diet, while (delta)('18)O values were (TURN)26 ('o)/oo more positive than (delta)('18)O values of ambient water. (delta)('15)N, (delta)D, and (delta)('18)O values were all found to be largely independent of temperature. Chitin biodegradation and carbonization did not produce isotopic changes, allowing archaeological and fossil chitins to be used in paleoecology and paleoclimatology.