Chemically-boring bivalves can mineralize more CaCO3 than they dissolve: the case of Leiosolenus patagonicus

Abstract

Mytilid bivalves in the genus Leiosolenus are widespread chemical borers of marine calcareous rocks and calcified biogenic structures. They are frequently acknowledged as significant agents of CaCO3 dissolution in these substrata. Yet, many studies estimating CaCO3 dissolution by these bivalves do not account for the fact that they also mineralize CaCO3 to form shells and, often, to line their boreholes, both of which could compensate for CaCO3 dissolution to a considerable extent. Here we evaluated whether the production of shells and ostensibly heavier borehole linings by Leiosolenus patagonicus compensates for the CaCO3 it dissolves during borehole excavation. Our estimates for two southwestern Atlantic, calcareous rocky shores indicate that CaCO3 mineralization by this species can substantially compensate or even exceed CaCO3 dissolution, with lining production accounting for most CaCO3 mineralization. Considering that Leisolenus species produce linings across diverse geographic regions and boring substrata, and that these linings could be heavier than those reported here for L. patagonicus, we posit that it should be a factor to consider when estimating net CaCO3 dissolution by these bivalves. Acknowledging CaCO3 mineralization and, particularly, lining production by these bivalves could help produce a more realistic picture of their roles in the carbonate system, carbon cycling, and the overall integrity of marine calcareous substrata.