The Application of Nanoindentation to Analyse the Mechanical Properties of Sea Urchin Teeth Subjected to the Effects of Ocean Acidification

• Main Author: Wang, Xiyang
• Other Authors: Dickinson, Michelle
• Format: Thesis
• Language: unknown
• Published: ResearchSpace@Auckland 2013
• Subjects: Ocean acidification
• Online Access: http://hdl.handle.net/2292/21183

Sea urchins belong to the Phlum Echinodermata family of marine animals and are dominant grazers, which helps in maintaining the levels of oceanic biomass. Sea urchins have a set of five teeth enclosed within a jaw-like structure known as the “Aristotle’s lantern”. The ability of self-sharpening is the most fascinating feature of the sea urchin tooth and it allows them to scrape and bore holes into rock for food. At present, as a potential biomimetic material, sea urchin teeth have obtained attention from engineers as a potential new cutting tool design. Due to a sequence of human activities, ocean acidification (OA) has become a global issue and marine creatures, ecosystems and world economies are under the threat due to OA. In this study the mechanical properties of sea urchin teeth and the effect of OA on them was investigated. In order to imitate natural conditions, a sea urchin feeding observation experiment was designed which recorded the feeding process mechanism. To further understand the effects of ocean acidification on urchin teeth, sets of teeth were immersed in sea water and adjusted using carbon dioxide solution to control the pH. The mechanical properties of the teeth were measured by using nanoindentation tests. Through data analysis and ESEM images, the structural characters of urchin teeth were observed and further understood as a function of their mechanical properties for both control teeth and those exposed to reduced pH sea water. Using the video footage of live urchins feeding, a theory behind the mechanism for self sharpening was determined. Results showed that a hardness gradient was found within the cross section of the very tip of the urchin teeth and the area with the highest magnesium concentration matrix structure had the greatest change under acidified seawater. Available to authenticated members of The University of Auckland.