Stable isotope ratio analysis for the authentication of sea urchin (Mesocentrotus nudus) from different culture areas in the North Yellow Sea, China

Abstract

Reliable methods of tracing the geographical origin of sea urchin are urgently needed for food safety and consumer health. To the best of our knowledge, the present study was the first attempt to trace the geographic origins of sea urchin by using stable isotope techniques. The δ13C, δ15N and δ18O values from the gonad and spine of sea urchins collected from five locations were analyzed. From the gonad samples, the δ13C values ranged from −22.07‰ to −18.37‰, the δ15N values ranged from 6.59‰ to 9.99‰, and the δ18O values ranged from 17.64‰ to 27.19‰. From the spine samples, the δ13C values ranged from −5.43‰ to −3.57‰, the δ15N values ranged from 7.95‰ to 13.66‰, and the δ18O values ranged from 33.99‰ to 40.15‰. The δ13C and δ15N values from the gonads differed significantly among samples from different geographic origins, but the δ18O values did not differ. The δ15N and δ18O values from the spines differed significantly among samples from different geographic origins, but the δ13C values did not differ. Both quadratic discriminant analysis (QDA) and the k-nearest neighbor (KNN) methods yielded low recognition of the δ13C, δ15N, and δ18O values from the gonad samples. However, higher accuracy was obtained using the stable isotope values from the spine samples combined with QDA or KNN methods. Moreover, the KNN methods gave more satisfactory accuracy, the initial, cross-validated, and predictive classification rates were 97.1%, 97.1%, and 93.3%, respectively. The C, N, and O stable isotope analysis of spine samples may be used to verify the geographic origin of sea urchins.