Culturing experiments exposed the scleractinian corals Porites lobata and Porites lichen to a mixture of dissolved chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), silver (Ag), cadmium (Cd), tin (Sn), mercury (Hg) and lead (Pb) in a wide concentration range for a period of more than a year. The aim was to examine whether the incorporation of heavy metals into the aragonitic skeleton of the corals is a direct function of their concentration in seawater. Therefore, the trace-element-to-calcium ratio (TE/Ca) in the coral aragonite precipitated during culturing was measured by Laser ablation ICP-MS in 2020. The measurement showed that all metals used here were measureable in the coral skeleton and only minor, non-systematic intra- and interspecies differences in the trace metal concentrations was found. A positive correlation between the TE/Ca values and the coral skeleton was found for Cr, Mn, Ni, Zn, Ag, Cd and Pb. Cu, Sn and Hg did not show any clear trend.
This dataset shows time resolved trace element-to-calcium values of coral colonies A to D cultured in the metal system along the measured Laser ablation ICP-MS scanning lines (Line XY stands for different Laser ablation lines measured at different positions at one respective coral colony) and values derived from the composite lines. Measurements were carried out from the top of the coral to the bottom and the distance starting from the top is indicated as “Elapse Time”. The energy density of the laser was set to 10 J/cm3, the laser spot size was 120 µm diameter and the stage moved 50 µm/s. Prior to every scan, a preablation pass with a spot size of 160 µm diameter was carried out to clean the cut surface of the coral skeleton. Culturing experiments were configured with two identically experimental aquaria. Four different coral colonies and two different species were used (Porites lobate Coral A-C, Porites lichen Coral D). All colonies were divided into subcolonies and growth control was performed with Alizarin Red S prior and during the experiment. One subcolony was placed in each experimental tank. The control aquarium remained unmodified while the trace metal concentration in the metal aquarium was elevated stepwise (Phase 1-4, Phase 1 = lowest metal concentration). The trace metal concentration in both tanks was monitored during the culturing period. After the experiment and more than 15 months later, specimens were cut again and the trace metal concentration in the coral skeleton was determined. It should be noted that coral D died 2.5 weeks after the exposure to the highest metal concentration in phase 4. TE/Ca values are processes as followed: (1) Time resolves raw intensities (in counts per seconds) for all isotopes measured were processed with the software Iolite (Version 4). The determination of element/Ca ratios was performed after the method of Rosenthal et al. (1999). High values of 25Mg, 27Al or 55Mn at the beginning of an ablation profile were related to contamination on the surface of the coral or remains of organic matter and these parts of the profiles were excluded from further data processing. (2) The NIST SRM 612 glass (Jochum et al., 2011) was used for monitoring and correction of the instrument drift. (3) The detection limit was defined by 3.3SD of the gas blank in counts per seconds for every element in the raw data. Only values above this limit were used for further analyses and no data below the LOQ (limit of quantification = 10SD) were interpreted. After processing the data with Iolite, an outlier detection of the TE/Ca ratios of the samples was performed. If trace metal values from deviated more than ±2SD from the average of the samples from the corresponding culturing phase, values were defined as outliers and discarded. (4) A composite line was calculated individually for all colonies consisting of the laser ablation measurements along the main growth axis of the coral (coral A line 1-3, coral B line 1-3, coral C line 2 + 3, coral D line 1). Laser ablation measurements along lines that were deviating from the main growth axis of the coral were not taken into account. Calculations were performed with QAnalyseries (Kotov and Paelike, 2018).
