Mineralogy and organic content are major predictors of shell loss in bivalves under reduced salinity, ocean freshening conditions

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..., , # Mineralogy and organic content are major predictors of shell loss in bivalves under reduced salinity, ocean freshening conditions

Dataset DOI: [10.5061/dryad.gtht76j0d](https://doi.org/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 shee...,