Being a bimineralic bryozoan in an acidifying ocean: Ocean acidification and bryozoans

Abstract

Strongly controlled calcification by bryozoans means that some species maintain complex skeletons formed of more than one mineral. Whether they are mainly intermediate-Mg calcitic with up to 50% aragonite, mainly aragonitic with small amounts of high-Mg calcite (>8 wt.% MgCO3), or formed of both high- and low-Mg calcites, preservation of sediments formed of these bimineralic bryozoan skeletons may be more at risk from ocean acidification than the majority of bryozoan sediments formed of monomineralic skeletons. An acid-bath immersion experiment on seven species reveals that three (Adeonella sp., Adeonella patagonica, and Adeonellopsis sp.) are more resistant to dissolution than the other four. Skeletal carbonate mineralogy appears to influence dissolution history very little: the most soluble aragonite and high-Mg calcite species, Adeonellopsis sp., was more highly resistant to dissolution than species dominated by low-Mg calcite. In the context of ocean acidification, it is likely that bryozoan skeletons with high surface area and small delicate morphologies are at greatest risk of dissolution, irrespective of mineralogical composition.