Shell trace elemental fingerprints of the deep-sea methane seep mussel Gigantidas childressi vary by depth, site, and shell growth region

Larval dispersal is a key driver of population persistence and resilience of numerous metapopulations and communities in marine ecosystems. Determining where and how larvae disperse in the deep sea is one of the most vexing challenges in deep-sea ecology. Laser ablation inductively coupled plasma mass spectrometry was used to evaluate the potential role of trace elemental fingerprints (TEFs) of deep-sea methane seep mussel Gigantidas childressi (n = 92 valves) in discriminating among collection depths, geographic regions (Gulf of Mexico and West Atlantic Margin; GOM and WAM), methane seep sites, and shell growth regions (larval VS settler shell). A priori permutational analyses of variance (PERMANOVA) discriminated among mussel valve TEFs across a depth gradient (650 m to 2206 m), among eight methane seep sites, and among shell growth regions. A priori canonical analyses of principal coordinates (CAP) generally matched and additionally discriminated TEFs among geographic regions. Results for post-hoc analyses on individual shell growth regions varied by statistical approach (PERMANOVA VS CAP) and by shell growth region (larval prodissoconch I and prodissoconch II VS settler dissoconch shell). Broadly, post-hoc PERMANOVA discriminated only among sites, while post-hoc CAP discriminated among all study factors. Discrimination among depths was mainly driven by the elemental ratio Ba:Ca. Discrimination among geographic regions was mainly by Ba:Ca and Sr:Ca. Discrimination among sites and shell growth regions was driven by all three elemental ratios analyzed (Ba:Ca, Sr:Ca, and Mg:Ca). Overall, shell TEFs show potential to discern spatial distribution of larval population pools. • Shell trace element fingerprints differ among methane seep sites and depths • Differences among groups usually correlate with barium and strontium-calcium ratios • Trace element fingerprints may be used to infer G. childressi larval population mixing