Annual M. mercenaria growth increment sclerochronology (1976-2020) from Virginia Coast Reserve LTER seagrass meadows

This study used a combination of field surveys and collections and sclerochronology laboratory methods to extract a 1976-2020 annual hard clam growth record from 51 seagrass-dwelling clams. Species-habitat associations and short-term experiments suggest that seagrass meadows enhance bivalve growth, yet this remains largely untested at ecologically meaningful spatiotemporal scales. We constructed a novel 45-year (1976-2020) shell-growth chronology from 51 hard clams (Mercenaria mercenaria) collected from a 20 km2 chronosequence of restored Zostera marina seagrass expansion across a coastal bay in Virginia, USA. SST anomalies alone explained 50-57 % of standardized growth index variance; a +1-degC anomaly increased shell deposition by ~3-4  In contrast, year-to-year meadow area, extent change, and distance to edge failed to meaningfully improve models at either the population (incremental R^2 less than 1%) or site scale, where SST effects exceeded habitat terms by two to three orders of magnitude. This study provides novel long-term empirical evidence that climate forcing can outweigh local habitat effects in seagrass-bivalve interactions--underscoring the dominant role of large-scale climate forcing in controlling and synchronizing coastal bivalve secondary productivity.