*** Combining isotopic analysis of bulk-skin and individual amino acids to investigate the trophic position and foraging areas of multiple cetacean species in the western South Atlantic***
Genyffer C. Troina1*, Philip Riekenberg2, Marcel T.J. van der Meer2, Silvina Botta1, Frank Dehairs3, Eduardo R. Secchi1
1 Laboratório de Ecologia e Conservação da Megafauna Marinha (ECOMEGA), Instituto de Oceanografia, Universidade Federal do Rio Grande - FURG, Avenida Itália km 8, Rio Grande, RS, Brazil. 
2 Department of Marine Microbiology & Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, Den Hoorn, 1790AB, The Netherlands. 
3 Analytical, Environmental and Geo-Chemistry Department (AMGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium

* Corresponding author: genyffertroina@gmail.com 
Orcid: https://orcid.org/0000-0001-5477-6064


***General Introduction***
This data set contains the  nitrogen stable isotope values from amino acids contained in marine mammal skin biopsies from the western South Atlantic

The data in this manuscript was produced in the Stable Isotope Laboratory in the Marine Microbiology and Biogeochemistry Department at NIOZ. 

***Test Equipment***
About 2–5 mg of 69 cetacean skin samples were processed for
analysis of δ15N in amino acids. This method is a modified version of the
method presented in Chikaraishi et al. (2007) and is described in detail
by Riekenberg et al. (2020). In short, samples were first acid hydrolyzed,
then derivatized into N-pivaloyl/isopropyl derivatives and analysed in
duplicate using a Trace 1310 gas chromatograph coupled to a DeltaV
Advantage isotope ratio mass spectrometer (Thermo Scientific, Bremen)
via a GC Isolink II, at the NIOZ Royal Netherlands Institute for Sea
Research (Texel, The Netherlands). This method allowed the measurement
of 13 individual amino acids: Phe, Lys, methionine (Met), tyrosine
(Tyr), threonine (Thr), serine (Ser), glycine (Gly), alanine (Ala), aspartic
acid (Asp), Glu, isoleucine (Ile), leucine (Leu) and valine (Val). Underivatized
amino acid δ15N values used for normalization were determined
via EA-irMS and were calibrated against IAEA-N-1 and IAEA-N-2 using
the secondary reference materials acetanilide #1 and urea #2 with a
precision of ±0.1‰. Both samples and standard δ15N values were
adjusted against an internal reference peak (norleucine), normalized to
account for derivatization, and then adjusted for linearity using a
‘scaling mix’ of 5 amino acids known to have a large range (􀀀 2.4‰–
61.5‰) composed of amino acid reference materials including Gly
(USGS65) and Val (USGS74) provided by Arndt Schimmelmann (Indiana
University; Schimmelmann et al., 2016). The precision for sample and
standard measurements was <0.5‰ with an average sample precision
(SD) of 0.24‰ for individual AAs, ranging between 0.2‰ for Leu and
0.3‰ for Thr. 

***Description of data***
lab; laboratory that analyzed the sample
lab_sample_id; lab sample ID
user_sample_id; User sample ID
sample_measurement_id; Bulk analysis of C and N 
collected_sample_mass; sample weight
instrumentation; Elemental analyzer
analysis_type; Bulk analysis of solid material
analysis_date; date and month of analysis
client_id; Who owns the sample
analytical_matrix; all tissues in this data set
primary_reference_material; Primary isotope reference material
preparation_step; sample preparations
preparation_step; sample preparations
material_type; generalized categories for sample ID of tissues
material_sample_id; Exact sample ID for tissue types
collection_source; All field samples
investigator_name; Philip Riekenberg
investigator_orcid; 0000-0002-6275-5762
investigator_email; phrieken@gmail.com
collection_locality; Wadden or North Sea
taxon_rank; ID is to species level
scientific_name; Genus species
amino acid_d15N; delta 15 N value for each amino acid
amino acid_error; standard deviation for the sample replicates of each amino acid
d15N_measurement_scale; against atmospheric N2
d15N_measurement_unit; per mille
d15N_error; standard deviation of the sample replicates for each amino acid analysis



