Given lower Оґ15N diet-tissue discrimination factors for large marine predators, removal of urea is required to elucidate accurate trophic position estimates and relative food web position of elasmobranchs and for diet reconstruction. In addition, the increase in Оґ15N values, decrease in %N and increase in C:N ratio indicate that lipid extraction is removing soluble urea. The Оґ13C data demonstrate that lipid extraction is required to remove lipids from elasmobranch muscle tissue given both intra- and inter- species variability. Field sampled animals (sampled immediately upon capture in the marine environment) showed a greater Оґ15N difference than animals sampled in the laboratory (sampled several hours after capture in the marine environment) (1.0 В± 0.5вЂ° and 0.4 В± 0.4вЂ° respectively), while estuarine sampled animals (sampled immediately) showed the smallest difference (0.1 В± 0.6вЂ°). There was no effect of increasing animal size on Оґ13C and Оґ15N difference (LEвЂ“BULK) for the two species examined. The mean and maximum observed increase in Оґ15N values were 0.6 В± 0.6вЂ° and 2.3вЂ°, respectively. The C:N ratio for these species also increased from unexpectedly low values of < 3.0 to ~ 3.0, the value expected for pure protein. For Оґ15N data, thirteen species showed a significant increase following lipid extraction and a concomitant reduction in total percent nitrogen (%N). The mean (В± SD) and maximum increase in Оґ13C values were 0.6 В± 1.2вЂ° and 5.9вЂ°, respectively. The mean (В± SD) Оґ13C values of eight out of twenty-one species significantly increased following lipid extraction with two species, the Greenland (Somniosus microcephalus) and whale (Rhincodon typus) shark, showing a marked increase (5.0 В± 0.4вЂ° and 3.3вЂ°, respectively). Through analysing paired Оґ13C, total %C, Оґ15N, total %N and C:N values of non-lipid extracted (BULK) and lipid extracted (LE) muscle samples from twenty-one elasmobranch species, we assessed whether lipid extraction was required: (i) to remove lipids given reported low lipid content and, (ii) to determine if Оґ15N values were affected and whether this relates to the retention of isotopically light urea by elasmobranchs. Given the known effect of lipid content on Оґ13C values and the potential effect of urea on Оґ15N values, examining the effects of lipid extraction, which can potentially extract both, is of particular importance for elasmobranch isotope ecology.

Tera dmesh swimwear