Boron isotope data from bivalves from 2022 tank experiment in the Gulf of Maine, USA

The boron isotopic composition (δ11Bc) of many marine carbonates provides insight into the pH at the site of calcification within biocalcifiers and, by extension, the pH of ambient seawater when the carbonate formed.

A 20.5-week flowthrough tank experiment was conducted in which four species of commercially important bivalves from the northwest Atlantic Ocean were grown in tanks with controlled pHT (pH 7.4 to 8.0) and temperature conditions (6 to 12 °C). A total of 106 shell samples from 99 individuals of adult and juvenile Arctica islandica (ocean quahog), juvenile Mercenaria mercenaria (northern quahog or hard clam), juvenile Mya arenaria (soft-shell clam), and juvenile Placopecten magellanicus (Atlantic sea scallop) were analyzed from this controlled experiment to assess the seawater pH, temperature, and growth rate controls on shell δ11Bc. Juvenile P. magellanicus and juvenile M. mercenaria demonstrated significant relationships (R≥0.60; p-value <0.006) between tank pHT and δ11Bc, suggesting potential utility as proxies for past ambient seawater pH. Conversely, the δ11Bc of juvenile A. islandica and juvenile M. arenaria did not yield a strong relationship with seawater pHT but instead yielded significant relationships with shell growth rate (linear extension), with a positive relationship for M. arenaria and a negative relationship for juvenile A. islandica. The δ11B results from the few (n=9) adult A. islandica shells measured show the most variability across the range of pH and temperatures (range of 16‰), and no significant relationship was found with seawater pH or growth rate. Despite rigorous oxidative cleaning of samples, the data suggest that adult A. islandica shells contain boron-rich organic phases resistant to traditional cleaning techniques.

The data on this site (summary file) include the average temperature, pH, and salinity used for the boron isotope analysis, in addition to the δ11B of the borate in water calculations, δ11B measured in the shells, the B/Ca ratio measured in the shells, and the delta pH values calculated using the above values.

Additional data include (temperature file) all temperature measurements from the tank experiment (every minute measurements) and daily averages. pH (pH file) and salinity (salinity file) data from weekly measurements are included. Data needed to perform the delta pH calculations are included (delta pH file).

The specimens grown in each tank that were used for boron isotope measurements are also included (boron specimens by tank file). This file specifies the number and species that were grown under the various tank conditions.