Mineralogy and organic content are major predictors of shell loss in bivalves under reduced salinity, ocean freshening conditions
Data files
Dec 10, 2025 version files 59.64 KB
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Data_file.xlsx
55.92 KB
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README.md
3.72 KB
Abstract
Ocean freshening due to increased precipitation and ice melting in a warming world poses a significant threat to marine calcifiers. The reduced availability of calcification substrates and an undersaturated calcium carbonate state challenge shell construction and maintenance. The corrosive potential of ocean acidification on biomineralised skeletons is well understood, but few studies have investigated the corrosive potential of significant and irregular freshwater input into marine habitats. To examine the susceptibility of invertebrate biocomposites to low salinity, we exposed blocks containing shell material of six bivalve taxa, representing different mineralogies and microstructures, to a salinity gradient (0–45‰) for 180 days. By measuring the loss of shell thickness, we revealed a significant correlation between dissolution and decreasing salinity. Significantly different amounts of shell thickness loss were observed across microstructures, revealing mineralogy and organic content as important predictors for dissolution. Aragonite layers lost significantly more shell thickness than calcite, and higher organic content retarded dissolution in aragonitic microstructures. Overall, shell dissolution in low salinities is greater than under the acidification predicted for end-of-century ocean pH conditions. The compromised integrity of marine invertebrate biomineralised skeletons because of ocean freshening is of critical concern with future predicted increases in precipitation and sea ice melt.
Dataset DOI: 10.5061/dryad.gtht76j0d
Description of the data and file structure
Resin blocks with shell fragments flush on the surface were placed in salinity treatments for 180 days before being removed. Shell thickness loss (dissolution) was measured using an ultra-high-definition digital microscope at magnifications of 100x, 400x, or 700x to measure the greatest change in depth (μm) relative to the resin surface.
Crystal width (to the nearest 0.1 µm) and variability (standard deviation) were measured from scanning electron micrographs of the exposed shell surfaces in the resin blocks using the ImageJ software.
Organic content was measured by thermogravimetric analysis.
Files and variables
File: Data_file.xlsx
Description: We have submitted an Excel file (Data_file.xlsx) with separate sheets that include the raw data for analyses of the resin blocks ("Resin_blocks_shell_loss") and separate sheets for calculating average Crystal size ("Crystal_size") and Organic content ("Organic content").
Variables
Resin_blocks_shell_loss
- Salinity: Salinity of treatment.
- Microstructure: Shell microstructure exposed in the resin, where two are the same, they are identified by a 1 or 2, depending on the species. Polymorphs indicated by (A) aragonite or (C) calcite.
- Microstructure_b: Shell microstructure (can be shared between species).
- Species: The species from which the microstructure was obtained.
- Mineralogy: Determines which calcium carbonate polymorph makes up the microstructure.
- Block ID: Identification of individual resin blocks.
- Measurement: Transect, i.e., measurement across the whole shell surface, or two-point, i.e., measurements taken from within the shell to the resin surface.
- Shell_loss: change in depth from resin surface to shell surface, measured in μm.
- Magnification: Magnification of the microscope at which measurements were made.
- Organics: Weight proportion of organic content in each microstructure.
- Mg_Ca: measured Mg/Ca ratio, only present in calcite, NA for aragonitic microstructures.
- Crystal size: measured 15 individual prisms in μm for each taxon. Calculated the average value and standard deviation.
- Tub: Treatment tub where the resin block was placed.
Crystal size
- Measurement: Measurement ID.
- Column headings: Species measurements were collected from.
- Observations: Average crystal width (to the nearest 0.1 µm) and variability (standard deviation) were calculated from 15 measurements of crystal width from scanning electron micrographs of the exposed shell surfaces in the resin blocks using the ImageJ software.
Organic content
- Taxon: Species ID.
- Organics (wt%): Weight proportion of organics in each species microstructure.
- SD: Standard deviation was calculated on samples of large enough size.
- Where samples were n=1 and standard deviation could not be calculated, blank cells are used to show no available data.
Code/software
Data can be viewed using Excel.
Access information
Other publicly accessible locations of the data:
Data was derived from the following sources:
- Raw data were collected between January 2024 and August 2024.
- Crystal widths of the crossed lamellar were measured using ImageJ from SEM images published in Figure 4 of Milano et al. [74] to take advantage of demarcated individual laths.
- Mg:Ca ratios were taken from Chadwick et al. [47].