Weakening mechanisms of the serpulid tube in a high CO2 world

Many benthic marine organisms produce calcium carbonate (CaCO3) structures for mechanical protection through a biologically controlled calcification process. However, the oceans are becoming unfavorable for calcification because of the stress associated with ocean acidification (OA) and asscoaited chemical changes such as declining saturation state of CaCO3 and seawater pH. This work studies the impacts of OA driven decreased pH on the calcareous tubes produced by the serpulid tubeworm, Hydroides elegans. Tubes grown under control and OA experimental conditions were measured for structural and mechanical properties; and their mechanical properties were further interpreted using finite element analysis (FEA). The near-future predicted pH value of 7.8 altered tube ultrastructure, volume and density, and decreased the mean tube hardness and elasticity by ~80% and ~70%, respectively. The crushing force required for breaking the tube was reduced by 64%. The FEA results demonstrated how a simulated predator attack may alter structural and mechanical properties and consequently shift the stress development and distribution in the tubes, causing a more concentrated stress distribution; and therefore leading to a lower ability to withstand attacks.

Li C., Chan V., He C., Meng Y., Yao H., Shih K. & Thiyagarajan V., in press. Weakening mechanisms of the serpulid tube in a high CO2 world. Environmental Science & Technology. Article (subscription required).

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