UC San Diego

In this dissertation, I present several tools to assist the community in making accurate and precise manipulations and measurements of carbonate chemistry parameters, which are essential for understanding, interpreting, and predicting the anthropogenic impact on the chemistry of our oceans. As the frequency of carbonate chemistry measurements increases with interest in the ocean's response to climate change, there is a continued need for confidence in the measurements to ensure data quality and consequent data usefulness. First, I explain the results of an international inter-laboratory comparison of various carbonate chemistry measurements. The majority of the results exhibit agreement within 0.5% of the assigned value for total alkalinity and total dissolved inorganic carbon, with significantly more variability in pH measurements. In many cases there is evidence of significant loss of CO₂ from the seawater samples, a particularly alarming bias given how critical these measurements are to the understanding of increasing anthropogenic carbon in our oceans. Carbonate chemistry measurements can also be compromised when taken from environments such as coastal and estuarine seawater, as well as laboratory cultures and aquaria, containing large numbers of suspended biogenic particles. The presence of these particles in a seawater sample may alter the results of the analysis for carbonate chemistry parameters including total alkalinity, total dissolved inorganic carbon, and pH. In this dissertation, I present the verification of a filtration method using a peristaltic pump and enclosed filter housing, which does not alter the dissolved CO₂ content of the seawater sample, and thus is suitable for filtration of samples before analysis. Finally, manipulation of carbonate chemistry in the laboratory is a crucial tool for studying the impacts of increasing CO₂ on organisms and communities, however is not always straightforward. I developed a carefully controlled aquarium system capable of manipulating the carbonate chemistry, oxygen levels, and temperature of seawater. The multi-stressor nature of the control is critical, particularly regarding the investigation of coastal ocean conditions, which are unique in the magnitude of range and temporal variability possible in these parameters. The aquarium system is dynamically controlled such that variability in pH may be introduced across many time scales. The novel tools presented in this dissertation for the manipulation and measurements of carbonate chemistry will assist in ensuring greater accuracy and understanding of the impacts of changes in carbon dioxide on our oceans