Elemental Distributions in Marine Bivalve Shells as Measured by Synchrotron X-Ray Fluorescence.

Area of Science:

• Marine biology
• Geochemistry
• Analytical chemistry

Background:

• Bivalve shells are archives of environmental conditions.
• Understanding elemental distribution in shells provides insights into marine ecosystems.
• Previous methods lacked the resolution to capture fine-scale elemental variations.

Purpose of the Study:

• To measure elemental concentrations in bivalve shells using synchrotron X-ray fluorescence.
• To investigate the heterogeneity of elemental distribution at various scales.
• To explore the potential of this technique for paleoclimate reconstruction.

Main Methods:

• Utilized synchrotron X-ray fluorescence (XRF) for elemental analysis.
• Achieved high sensitivity (down to 1 ppm) and spatial resolution (as low as 8 µm).
• Analyzed shells from Mercenaria mercenaria, Mya arenaria, and Argopecten irradians.

Main Results:

• Detected heterogeneous distribution of elements (Mn to Pb) at both large (mm) and small (µm) scales.
• Observed variations in shell layer composition and seasonal strontium (Sr) concentration changes.
• Identified elevated iron (Fe) levels at specific shell layer boundaries in Mercenaria mercenaria.
• Demonstrated temporal variations in Sr concentration over months, correlating with water temperature.

Conclusions:

• Synchrotron XRF is a powerful tool for detailed elemental mapping in bivalve shells.
• Shell elemental composition reflects both short-term environmental changes and long-term growth patterns.
• The technique holds promise for reconstructing historical marine environmental conditions, including water temperatures.