Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

A complete description of the collection and experimental methods is available in Grottoli et al. (2010). In brief, six A. wellsi sclerosponges were identified between 11.5 and 18 m depths along the wall at Short Drop Off, Palau. The specimens were stained with Alizarin Red on 26 July 2001, re-cemented onto the reef at a common depth of 11 m depth using Splash Zone marine epoxy, and allowed to grow out past the stain line for 2 years. In Saipan, three A. wellsi identified at 6 m depth and four A. willeyana sclerosponges identified between 7 and 9 m depth were stained with Alizarin Red on 15 July 2001, re-cemented onto the reef at a common depth of 8.3 m depth with marine epoxy, and allowed to grow out past the stain line for 2 years. On 15 July 2003 and 11 July 2003 all of the specimens were collected from Palau and Saipan, respectively, and were returned to the lab for further analysis.

In the laboratory, each specimen was cut down its major growth axis, cleaned with deionized water, and dried at 60°C for 3 days. The sclerosponge skeletons were then sampled in two ways for elemental analysis. First, bulk measurements spanning the entire two-year common time period established by the stain lines were obtained from each specimen. Each bulk skeletal sample was milled from the growing edge to the stain line using a Dremmel tool fitted with a diamond-tipped dental drill bit. Second, high-resolution samples were milled at 0.5 mm increments using a Merchantek Micromill from two A. wellsi specimens from Palau, one A. wellsispecimens from Saipan, and one A. willeyana specimen from Saipan from the growing edge to the stain line.

Sample Solutions and Standards: All solutions were made with MilliQ water (18 MΩ; Millipore, MA) and ultrapure reagents unless otherwise noted. All labware was pre-cleaned with 5% v/v HNO₃, 20% v/v HCl and MilliQ water for a minimum of 10 hours each prior to sample handling in a Laminar Flow Exhausting Hood. Gravimetric standards were used to make calibration curves for P, Pb, Ba, and Ca. Stock standard solutions (CPI International) were diluted with ultrapure 2% v/v HNO₃ to concentrations that matched expected range of sample concentrations.

Sample Preparation: Bulk sclerosponge samples of approximately 10 mg were pre-cleaned for elemental analysis following methods described in Matthews et al. (2006). In brief, samples were ultrasonicated in MilliQ water, oxidized in a solution of 50:50 0.2M NaOH and 30% H₂O₂, reduced using hydrazine buffered in 50:50 mixture of 30% NH₄OH and 0.25M (NH₄)2C₆H₆O₇, and leached in 0.001M HNO₃, with sub-boiling heat baths and ultrasonication, and multiple MilliQ water rinses between each step. Following cleaning, samples were dissolved in 6 mL of 2% v/v HNO₃. High-resolution 0.5 mg samples were prepared in the same method with the exception that they were dissolved into 2.5 mL of 2% v/v HNO₃.

Elemental Analyses: Measurements were carried out on a Thermo Finnigan Element 2 ICP-SFMS using low (m/∆m = 300) resolution (with the exception of P at medium (m/∆m = 4000) resolution) and operated in E-scan mode with an uptake rate of 100 µL/min. Internal standards of Co (for Ca and P), Rh (for Ba), and Bi (for Pb) were used to correct for signal drift over the course of the run, blank corrected, and then concentrations calculated using the calibration curves from the gravimetric standards. For quantification, ⁴³Ca, ³¹P, ²⁰⁸Pb, and ¹³⁸Ba were used. At least one additional isotope of each element was monitored to check for interferences. P, Pb, and Ba concentrations were standardized to the measured Ca concentrations. The %RSD for P/Ca, Pb/Ca, and Ba/Ca are 3.7%, 7.2%, and 5.5% or better, respectively, based on repeated measurements of a check standard throughout the sequence of sample measurements.

BCO-DMO Processing:
- renamed fields;
- replaced "n/a" with "nd" as missing data value;
- split latitude and longitude into separate columns;
- converted latitude and longitude from degrees and minutes to decimal degrees (rounded to 3 decimal places);
- replaced commas with semi-colons in Location_country column.

NSF Award Abstract:
Proxy records are extremely useful for reconstructing paleoceanographic/ paleoclimate conditions and hence understanding oceanographic and climate change, although these data must be well-calibrated. However, proxy tools to evaluate annual-to-centennial timescale variability of the stable isotopic composition of dissolved inorganic carbon and oxygen in seawater over the past several centuries in the Pacific or to evaluate these variables and seawater temperature across depth have not been fully developed. The western Pacific plays a large role in tropical and global climate and is therefore an ideal location to pursue this research.

A scientist at the University of Pennsylvania will quantitatively calibrate the sclerosponge, Acanthocheatetes wellsi, skeletal d13C, d18O, and strontium/calcium (Sr/Ca) to evaluate calibrated proxy records on annual-to-interdecadal timescales. The calibrations will then be applied to two high-resolution 50-year stable isotope and Sr/Ca records and the interannual-to-interdecadal timescale variability in the longer records will be evaluated by comparing them to available instrumental, satellite, and model output data.

The results will be a valuable tool for constraining existing carbon uptake models, initializing and testing ENSO models, and generally increasing our knowledge of the natural spatial and temporal variability in d13CDIC, d18Osw, and seawater temperature at the surface and across depth in the tropics.