Abstract:

Biominerals are biologically produced minerals that allow different species to build their skeletons. My research focuses specifically on marine calcifiers that produce calcium carbonate (CaCO3) shells. Ocean acidification poses a problem to these calcifiers as it makes seawater more acidic and reduces biologically important ions needed to make their shells. However, not all species respond the same to ocean acidification, making it important to understand how ocean acidification will affect these organisms in the future.

Organisms calcify from an internal fluid pool called the calcification fluid which is, to varying degrees, separated from seawater to achieve supersaturation for crystal nucleation. My research takes advantage of the shell boron isotopic signature which acts as a proxy for the pH of the internal calcification fluid. These measurements give us an understanding of whether or not these organisms have the ability to modify their internal calcification fluid from seawater, which is especially important to understand in the face of ocean acidification. Additionally, I measure different shell elemental ratios that are commonly used as proxies to understand how the biomineralization strategies may skew elemental incorporation in the shell.

Each chapter of my thesis uses case studies of different types of marine invertebrates to answer these questions. The first chapter makes use of a laboratory experiment that exposed four species of coralline algae to different future OA scenarios. My second chapter compares two ecologically and commercially important bivalve species, the calcitic eastern oyster and the aragonitic ocean quahog. My findings are important to understanding how these organisms will be affected by ocean acidification in the future and the use of these taxa as proxy archives in paleoclimate research.