Climate change impacts on the serpulid tubeworm Hydroides elegans : a biomineralization perspective

• Main Authors: Chan, Bin-san, 陳辯宸
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Hong Kong (Pokfulam, Hong Kong) 2013
• Subjects: Biomineralization; Ocean acidification - Environmental aspects; Tube worms; Ocean acidification
• Online Access: https://doi.org/10.5353/th_b5177307; http://hdl.handle.net/10722/196468

Atmospheric carbon dioxide (CO2) has increased due to human activity from a pre-industrial value of about 280 ppm to the present level of 399 ppm. The ocean acts as an important natural carbon sink that effectively removes 1/3 of this anthropogenic CO2 from the atmosphere, buffering global warming effects. However, the dissolution of CO2 causes a dramatic change in seawater chemistry and ultimately results in the phenomenon commonly known as "ocean acidification" (OA). As a consequence, the pH value and the saturation states for calcium carbonate decline in the surface seawater, posing a threat to calcareous marine organisms that build their shells using exquisite biomineralization mechanisms. Biological minerals produced by marine organisms are compositionally and structurally more complex than geological minerals. Although changes in biomineral formation in response to OA has been intensively investigated, the features of calcified products in terms of their composition, architectures and mechanical properties have been overlooked in climate change research. The tubeworm is a favourite marine model organism in larval biology. Its life cycle is well understood hence provides a good opportunity to study OA impacts on the stochastic early life. In addition, the model enables comprehensive observation of the sophisticated biomineralization events. In this thesis, four studies on the biomineralization of Hydroides elegans, using a multidisciplinary collaborative approach combining larval biology and material science were conducted. (1) The tube mineral composition at different juvenile stages (4, 11, 18, 25 days) were characterized. (2) The impacts of different predicted OA scenarios (pH 8.1, 7.9, 7.6, and 7.4) on the resultant calcification products were compared. (3) A multiple-stressor investigation of OA (pH 8.1 and 7.8), reduced salinity (33 ‰ and 27 ‰) and increased temperature (25 °C and 29 °C) was conducted to further determine the more environmentally realistic OA impacts. (4) Calcification sites were ...