Dataset DOI: 10.5061/dryad.h1893201z

Description of the data and file structure

This dataset contains micro-computed tomography (microCT)-derived relative skeletal-density transects, LA-ICP-MS elemental measurements, in-situ temperature data for the study interval (4 mo.), and manually and computationally derived growth-increment-width and growth rate data from rhodolith branches (fruticose thalli).

To calibrate growth band periodicity, skeletal density, and element-incorporation patterns, rhodoliths were collected by snorkelers from 1 m water depth on 6 March 2024 from the exposed side of Al Fahal, a shallow reef flat in the Saudi Arabian Red Sea (22°17'51.37"N, 38°57'43.90"E).

Samples were stained with alizarin red and redeployed for approximately four months (Spring). Following recovery, rhodoliths were air-dried. Branches from all axes of each rhodolith were separated using a chisel, embedded lengthwise in 1-inch-diameter epoxy stubs, polished, and imaged under a stereomicroscope in preparation for light microscopy, microCT scanning, scanning electron microscopy (SEM), and laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).

AFE5-1 was microCT scanned at 9-10 µm resolution and transects of relative derived skeletal density were extracted perpendicular to the growth axis of individual branches (post_stain_growth_1000_1.csv, post_stain_growth_1000_2.csv, post_stain_growth_1000_3.csv, post_stain_growth_1000_4.csv). 3D image processing was done using Avizo image software. Each ‘post_stain_growth’ file contains two columns, the first of which is distance along the branch in µm, and the second of which is relative derived skeletal density, a unitless relative greyscale value extracted along a transect through the central axis of the rhodolith branch. Relative skeletal density is derived from microCT greyscale intensity and is not calibrated to an absolute density scale.

Major and minor element concentrations were measured in individual rhodolith branches (n = 7) using LA-ICP-MS (branch1_laser.csv, branch2_laser.csv, branch3_laser.csv, branch4_laser.csv, branch5_laser.csv, branch6_laser.csv, and branch7_laser.csv) at the Max Planck Institute for Chemistry (Mainz, Germany). All analyses were performed with a solid-state New Wave UP-213 laser system (213 nm) coupled to a single-collector sector-field ThermoFisher Scientific ELEMENT2 mass spectrometer. Laser spots (n = 320 total; 40 μm diameters) were measured across each selected rhodolith branch following the apex of each visible growth increment from the alizarin stain to the end. Each branch[n]_laser.csv file contains the tabular LA-ICP-MS data for one rhodolith branch and retains the original analytical column headings. Further details on analytical procedures, calibration, data reduction, and interpretation are provided in the associated manuscript and Supplementary Information.

Daily mean in-situ temperature data for the study interval (Temperature.csv) were collected using Hobo Pendant UA-64-001 loggers placed 1–2 m away from the cage site and shaded beneath PVC covers to minimize solar heating effects (Rich et al., 2024). The sensors have an accuracy of ±0.54 °C and were calibrated against SBE‑56 loggers.

'IncWidth_Calculated_1.csv' and 'IncWidth_Calculated_2.csv' contain calculated growth increment width data derived from the relative derived skeletal density transects in the post_stain_growth files. Repeat transects were used because they capture slightly different density facies within individual branches. Growth rate was inferred for calculated increment widths using the assumption that growth rate is inversely related to skeletal density: more compact cell chambers correspond to relatively higher-density regions along a rhodolith branch. 'IncWidth_Manual.csv' contains manually measured growth increments. A growth increment was defined visually as one light/dark cycle observed in the approximately 9–10 µm voxel-resolution microCT scans. Growth rate was calculated using the same approach applied to the calculated increment-width data.

Further details on increment identification, density processing, growth-rate calculation, and interpretation are provided in the associated manuscript and Supplementary Information.

Empty cells within the deposited data tables indicate that no value is reported for that field and record; they should not be interpreted as numerical zeros. In the LA-ICP-MS files, an internal empty cell may indicate a result below the detection limit or a value excluded as an outlier during data reduction.

Values recorded as 0 are valid numerical values. A value of 0 indicates that the relevant measurement, calculated quantity, or data field had a value of zero; it does not indicate missing data.

Trailing blank rows and cells at the bottoms of the original Excel worksheets are spreadsheet-layout artifacts. 

Code/software

Code for reproducing DTW analysis is available on Github at https://github.com/lenayueshali/Rhodo-pipeline.

Access information

Other publicly accessible locations of the data:

• NA

Data was derived from the following sources:

• MicroCT scans, LA-ICP-MS spot transects, Hobo Pendant UA-64-001 temperature logger.