Dataset: Bulk and CSIA-AA stable isotopes in sinking POM and proteinaceous deep-sea coral skeletal material

Location description: 
Central California Coast, Monterey Bay.

Sinking particles were collected at station M2 (36.697˚N, 122.378˚)

The trap was deployed at 1200 m depth 

Two bamboo coral specimens (Isidella sp.),  were collected in Monterey Canyon (36.747˚N, 122.022˚W) in 2007 at depths of 915 m and 835 m
Methods & Sampling:

Sinking particles were collected at station M2 (36.697˚N, 122.378˚W; Fig. 1 of Shen et al., 2021) using an acid-cleaned cone-shaped Honjo Mark VI sediment trap. The trap was deployed at 1200 m depth (~500 m above the seafloor) from January 1999 through December 2004. The trap was outfitted with 13 collection cups that contained preservatives (3.0 mM of mercury chloride and > 5 g/L of sodium chloride) and rotated every 14 days. There were gaps in the sampling due to technical issues with sediment trap program or trap retrieval. The collection and handling of samples followed the procedures described in Castro et al. (2018). The oven-dried samples were ground in an agate mortar and stored in polyethylene vials or polycarbonate tubes at room temperature in the dark until elemental and isotopic analyses.

From the two Isidella app specimens, polyp and tissue material was separated from skeletons upon collection, and the samples were washed in seawater and rinsed in freshwater prior to air drying. An organic node (6-8 mm thick) was removed from near the basal attachment of each coral skeleton and decarbonated in 10% HCl. Using scalpel and forceps, organic peels (0.4 -0.5 mm thick) were dissected and then rinsed in Milli-Q water and dried. Based on bomb-14C dating, the growth rate of Isidella in Monterey Bay was estimated to be 0.14 mm/yr; thus each peel represents a 3-4-year time window. We present data from only the second and third peels from each coral because they represent the best temporal match to the sediment traps data (1999-2004).

Sediment trap samples were separated into aliquots for bulk δ13C and δ15N analysis. Aliquots for δ13C analysis were weighed (~10 mg) into silver boats and acidified by immersion in 6-8% sulfurous acid (H2SO3) followed by repeated rinses with Milli-Q water and drying at 60˚C overnight. The other aliquots for δ15N analysis (~10 mg) were not pre-treated. Coral peels were acidified during the previous preparation (section 2.1) and did not undergo any further pre‑treatment. Approximately 0.15 mg of coral peels was used for bulk δ13C and δ15N. Bulk isotope analysis was performed at the UC Santa Cruz Light Stable Isotope Laboratory using a Carlo Erba 1108 elemental analyzer coupled to Thermo Finnigan Delta Plux XP isotope ratio mass spectrometer following standard procedures (https://websites.pmc.ucsc.edu/~silab/index.php). Isotopic values were corrected for sample size and instrumental drift and were reported in units of per mil (‰) relative to Vienna PeeDee Belemnite (VPDB) and air for δ13C and δ15N, respectively. Analytical precision as monitored with acetanilide was <0.2‰ for δ13C and δ15N.

Approximately 10-15 mg of dried sediment trap and coral material was used for amino acid δ13C and δ15N analyses. Hydrolysis, purification, and derivatization followed previously established protocols in batches of 5-7 samples. An AA mixture of known δ13C and δ15N values and an in-house biological reference standard (homogenized cyanobacteria) was analyzed along with each sample batch. The AA mixture was used to calibrate the δ13C and δ15N results. The cyanobacteria reference, processed in the same way as samples, was used to monitor the consistency of wet chemistry and instrumental analysis (Table EA1 of Shen et al., 2021). δ13CAA and δ15NAA values were determined using a Thermo Trace Ultra gas chromatography (GC) coupled with a Finnigan MAT DeltaPlus XL IRMS at UCSC SIL. Samples were injected in triplicate, bracketed by triplicate injections of the calibration standard. Final δ13CAA values were corrected for the added derivatizing reagents, and final δ15NAAvalues were corrected based on the offset between known and measured δ15NAA values of the calibration standard. The standard deviation of replicate injections for individual AAs in the samples ranged from 0.2‰ to 0.5‰ for δ13C and from 0.1‰ to 0.6‰ for δ15N. The relative abundance (mol%) of amino acids was determined from peak areas measured during d15N analysis. Peak area response factors for individual AAs were calculated from the known-concentration external standards and then applied to sample peak areas to derive molar abundances.

One cyanobacteria standard was analyzed during each batch of sample measurement. Data for each batch are reported as average and standard deviation of 3 injections. _AVG and _STD columns refer to the average and standard deviation value of the entire standard set (n = 8 for C; n = 6 for N). 

Carbon stable isotope values are reported in per mil notation relative to V-PDB.

Nitrogen stable isotope values are reported in per mil notation relative to AIR.

Instrument description:

Bulk isotope analysis was performed at the UC Santa Cruz Light Stable Isotope Laboratory using a Carlo Erba 1108 elemental analyzer coupled to Thermo Finnigan Delta Plux XP isotope ratio mass spectrometer following standard procedures (https://websites.pmc.ucsc.edu/~silab/index.php).

CSIA-AA δ13CAA and δ15NAA values were determined using a Thermo Trace Ultra gas chromatography (GC) coupled with a Finnigan MAT DeltaPlus XL IRMS at UCSC SIL.

Abbreviation/Terminology Description:

AA or AAs = Amino acids
Ala = Alanine
Asx = Asparagine + aspartic Acid
AVG = Average
Baseline isotope values = Refer to the source nitrogen d15N value or primary production d13C value
CSI-AA = Compound-specific isotope analysis of amino acids
CSI-AA-based proxies = Refer to d13CPhe, d13CEAA, d15NPhe, d15NSrcAA, or/and TPCSI-AA
CSI-AA baseline proxies = Refer to d13CPhe, d13CEAA, d15NPhe or/and d15NSrcAA
CSI-AA values =  Refer to C and N isotope values of amino acids in general
DI = Degradation index (based on mol% values of protein AAs)
DIC = Dissolved Inorganic Carbon
EAA = Essential amino acids (Thr, Ile, Val, Phe, Leu, Lys)
Exported = TP Trophic position of export production
GC-IRMS = Gas chromatography isotope ratio mass spectrometry
Glx = Glutamine + Glutamic acid
Gly = Glycine
HCl = Hydrochloric acid
H2SO3 = Sulfurous acid
Ile = Isoleucine
Leu = Leucine
Lys = Lysine
NEAA = Non-essential amino acids (Gly, Ser, Asx, Glx, Pro, Ala)
Phe = Phenylalanine
POC = Particulate organic carbon
POM = Particulate organic matter
Pro = Proline
Ser = Serine
Source = nitrogen Inorganic nitrogen used by primary producer (e.g., N2 or nitrate)
SrcAA = Source amino acids (Phe, Lys)
SV = Sum of variance (based on d15N values of trophic amino acids)
STD = Standard deviation
TDF = Trophic discrimination factor
Thr = Threonine
TP = Trophic position
TPCSI-AA = Trophic position estimated from d15N values of Glu and Phe
TPskeleton = TPCSI-AA values of coral skeletons
TrAA = Trophic amino acids (Glx, Asx, Ala, Leu, Ile, Pro, Val)
Val = Valine
VPDB = Vienna PeeDee Belemnite
d13CEAA = Mean d13C value of the six essential amino acids
d13CNEAA = Mean d13C value of the six non-essential amino acids
d15NSrcAA = Mean d15N value of the two source amino acids
d15NTrAA = Mean d15N value of the seven trophic amino acids
d13Cexport = production Bulk d13C value of sediment trap material (i.e., sinking particles)
d15Nexport = production Bulk d15N value of sediment trap material (i.e., sinking particles)