The Impact of Algal Biofilms on the Microenvironment of Concrete Substrates
Regan, Victorialyn R.
Coastal zones, ecologically and economically important areas, are projected to experience higher rates of warming and seawater acidification in the coming years. Ectothermic calcifying organisms such as mussels may be particularly vulnerable to these trends since bivalve larvae must transition from pelagic larvae to benthic juveniles, and are sensitive to environmental conditions during this critical development phase. In addition, the settlement process is both highly specific and driven by a number of variables, including pH levels and the presence of an algae biofilm. In order to better understand these relationships, two types of concrete blocks, standard concrete tiles and calcium carbonate-fortified discs, were deployed in a sheltered coastal harbor for up to six weeks. Block pairs were removed after one, five, and six weeks, and a microelectrode pH probe was used to characterize the microenvironment promoted by the algae and biofilm growth. It was found that, overall, concrete appeared to have a local effect on pH; while no significant change was observed across the concrete tiles, the pH increased significantly close to the surface of the calcium carbonate discs. However, this increase in basicity appeared to be less pronounced the longer the disc was deployed, indicating other variables may have had a stronger influence on the pH than the presence of algae. Future work must therefore investigate the effects of organismal presence, wave action, and block shape or texture on pH gradients to better characterize these results and better understand how they may affect the settlement of marine life.
vii, 31 p.
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