Investigating climate-induced bivalve growth synchrony across coastal ecosystems: a sclerochronological approachMacroecology

Michael Cornish¹, Max C. N. Castorani¹, Kyle Emery²

¹University of Virginia, USA - ²University of California, Santa Barbara, USA

Climate change is intensifying the influence of large-scale environmental drivers—such as sea surface temperature (SST)—that can synchronize population dynamics across vast regions. In coastal ecosystems, filter-feeding bivalves can strengthen these climate-driven effects through their phytoplankton-fueled secondary productivity that links local food webs to broader-scale oceanographic forces (i.e., benthic-pelagic coupling). Here, we use sclerochronology (bivalve shell-sectioning and growth chronology construction) techniques and wavelet synchrony models to investigate long-term growth rates in three bivalve species—the rock-boring clam (Parapholas californica) from giant kelp forests and Pismo clams (Tivela stultorum) from nearby sandy beaches on the west coast of North America (California, USA), and hard clams (I) from eelgrass meadows on the mid-Atlantic coast (Virginia, USA). We found that bivalve growth trends are strongly synchronized by climate, with the North Pacific Gyre Oscillation’s influence on coastal-upwelling-fueled phytoplankton supply emerging as the dominant driver on the California coast while interannual SST mediated clam productivity on the Virginia coast. Our results underscore that intensified climate forcing can overwhelm local environmental heterogeneity, potentially reducing regional population stability by weakening portfolio effects (e.g., environmental refugia availability). Hence, bivalves’ roles in benthic-pelagic coupling are vulnerable to ongoing global change, highlighting the importance of understanding the consequences of widespread, climate-induced growth synchrony across coastal ecosystems.