The Effects of Ocean Acidification and Hypoxia On Elemental Incorporation Into the Otoliths of Estruarine Fish in the Gulf of Mexico

Otoliths are bones found in the ears of fish. Fish lay down layers of bone onto otoliths daily, and elements from the environment are incorporated into otoliths. The suite of elements in otoliths acts as natural markers, and by examining these elements, movements, stock structure, and the location of fish over time can be determined. The integrity of this tracking method can be compromised by changes in water chemistry, such as lower pH (acidification) and lower concentrations of dissolved oxygen (hypoxia). While ocean acidification and hypoxia have been shown separately to affect elemental incorporation in marine organisms, the effects of both parameters have not been examined together in a controlled setting. The purpose of this study is to examine potential synergistic or antagonistic effects of simultaneously lowered pH and DO on otoliths of Atlantic croaker, an important estuarine fish. In this study Atlantic croaker will be exposed to  pH and DO levels predicted for the year 2100, and we will use laser-ablation inductively-coupled mass spectrometry to investigate changes in elemental composition of otoliths under future conditions.