Investigating controls of shell growth features in a foundation bivalve species: seasonal trends and decadal changes in the California mussel

[摘要] Marine bivalve mollusk shells can offer valuable insights into past oceanographic variability and seasonality. Given its ecological andarcheological significance, Mytilus californianus (California mussel) presents the opportunity to examine seasonal and decadal changesrecorded in its shell over centuries to millennia. While dark–light growth bands in M. californianus shells could be advantageous forreconstructing past environments, uncertainties remain regarding shell structure, environmental controls of dark–light-band formation, and theamount of time represented by a dark–light pair. By analyzing a suite of M. californianus shells collected in 2002, 2003, 2019, and 2020from Bodega Bay, California, we describe the mineralogical composition; establish relationships among the growth band pattern, micro-environment, andcollection season; and compare shell structure and growth band expression between the archival (2002–2003) and modern (2019–2020) shells. Weidentified three mineralogical layers in M. californianus : an outer prismatic calcite layer, a middle aragonite layer, and a secondaryinner prismatic calcite layer, which makes M. californianus the only Mytilus species to precipitate a secondary calcitelayer. Within the inner calcite layer, light bands are strongly correlated with winter collection months and could be used to reconstruct periodswith moderate, stable temperatures and minimal upwelling. Additionally, modern shells have significantly thinner inner calcite layers and morepoorly expressed growth bands than the archival shells, although we also show that growth band contrast is strongly influenced by themicro-environment. Mytilus californianus from northern California is calcifying differently, and apparently more slowly, than it was20 years ago.

[学科分类] 大气科学