Urea and lipid extraction treatment effects on δ¹⁵N and δ¹³C values in pelagic sharks

Abstract

Given the mean change in δ(15)N(1.2 ± 0.6‰) and δ(13)C values (0.7 ± 0.4‰) across pelagic shark species, it is recommended that muscle tissue samples be treated with LE+DW to efficiently extract both urea and lipids to standardize isotopic values. Mathematical normalization of urea and lipid-extracted δ(15)N(LE+DW) and δ(13)C(LE+DW) values using the lipid-extracted δ(15)N(LE) and δ(13)C(LE) data were established for all pelagic shark species.

Effects of lipid and urea extraction on stable isotope values (δ13C and δ15N) of two batoids: A call for more species‐specific investigations

“…Thus, high urea concentrations in elasmobranch tissues lower δ 15 N values, and this can result in an underestimation of trophic positions (Kim and Koch ; Carlisle et al ). Experimental studies examining the influence of urea on elasmobranch δ 15 N have illustrated that urea‐extracted tissues generally have higher δ 15 N and C:N ratios relative to untreated tissues although results are not consistent across all species (Kim and Koch ; Li et al ; Burgess and Bennett ; Carlisle et al ). The increase in C:N ratio following urea‐extraction has important implications for assessing tissue lipid content based on the C:N ratios.…”

Trophodynamics as a Tool for Understanding Coral Reef Ecosystems

“…Recently, Matley et al (2016) showed that diet tissue determination factors and turnover rates measured for temperate species may not apply to tropical species, as δ 15 N enrichment was lower than published values for a slowgrowing predatory reef fish. In larger predatory species such as sharks, care in sample preparation is also necessary as urea retention without extraction can severely affect values, which is often not a common method employed for stable isotope analysis (Li et al, 2016). The physical and biogeochemical nature of a habitat can also have large effects on trophic community structure even at a fine scale.…”

Quantifying ontogenetic stable isotope variation between dermis and muscle tissue of two pelagic sharks

“…Dermis was then freeze-dried at −55°C for 48 h using a Christ Alpha 1-4 LD plus Freeze Dryer (Martin Christ), and each sample was homogenized using a Retsch Mixer Mill MM 400 (Retsch). Sharks maintain urea and trimethyl amine oxide in their tissues for osmotic balance, which are considered to be 15 N-depleted and may also affect δ 13 C values (Fisk et al 2002, Li et al 2016. Consequently, urea was removed from muscle tissue using a standard water washing technique (Kim & Koch 2012, Li et al 2016).…”

“…Sharks maintain urea and trimethyl amine oxide in their tissues for osmotic balance, which are considered to be 15 N-depleted and may also affect δ 13 C values (Fisk et al 2002, Li et al 2016. Consequently, urea was removed from muscle tissue using a standard water washing technique (Kim & Koch 2012, Li et al 2016). For δ 15 N analysis, all muscle tissue samples were urea-extracted, while for δ 13 C, both urea and lipids were removed using combined water washing and standard chloroformmethanol extraction (Li et al 2016).…”

“…Consequently, urea was removed from muscle tissue using a standard water washing technique (Kim & Koch 2012, Li et al 2016). For δ 15 N analysis, all muscle tissue samples were urea-extracted, while for δ 13 C, both urea and lipids were removed using combined water washing and standard chloroformmethanol extraction (Li et al 2016). Tissue samples were then freeze-dried to remove remaining solvent and divided into approximately 1 to 1.5 mg subsamples for stable isotope analysis using an IsoPrime 100 isotope ratio mass spectrometer (IsoPrime) and a vario ISOTOPE cube elemental analyzer (Elementar …”