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Marine Ecology Progress Series

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MEPS 656:193-205 (2020)  -  DOI:

Little evidence that lowering the pH of concrete supports greater biodiversity on tropical and temperate seawalls

Amanda R. Hsiung1,#, Wen Ting Tan1,#, Lynette H. L. Loke1,4,*, Louise B. Firth2, Eliza C. Heery1,5, James Ducker2, Victoria Clark2, Y. Shona Pek3, William R. Birch3, Ambert C. F. Ang1, Rania S. Hartanto1, Tiffany M. F. Chai2, Peter A. Todd1

1Experimental Marine Ecology Laboratory, Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Block S3, Singapore 117557
2School of Biological and Marine Sciences, University of Plymouth, Plymouth PL4 8AA, UK
3Institute of Materials Research & Engineering, 2 Fusionopolis Way, Innovis, Singapore 138634
4Present address: Department of Earth and Environmental Sciences, Macquarie University, North Ryde, New South Wales 2109, Australia
5Present address: Friday Harbor Laboratories, University of Washington, 620 University Rd, Friday Harbor, Washington 98250, USA
#These authors contributed equally to this work
*Corresponding author:
Advance View was available online July 9, 2020; subsequently updated August 14, 2020

ABSTRACT: Concrete is one of the most commonly used materials in the construction of coastal and marine infrastructure despite the well known environmental impacts which include a high carbon footprint and high alkalinity (~pH 13). There is an ongoing discussion regarding the potential positive effects of lowered concrete pH on benthic biodiversity, but this has not been investigated rigorously. Here, we designed a manipulative field experiment to test whether carbonated (lowered pH) concrete substrates support greater species richness and abundance, and/or alter community composition, in both temperate and tropical intertidal habitats. We constructed 192 experimental concrete tiles, half of which were carbonated to a lower surface pH of 7-8 (vs. control pH of >9), and affixed them to seawalls in the United Kingdom and Singapore. There were 2 sites per country, and 6 replicate tiles of each treatment were collected at 4 time points over a year. Overall, we found no significant effect of lowered pH on the abundance, richness, or community assemblage in both countries. Separate site- and month-specific generalised linear models (GLMs) showed only sporadic effects: i.e. lowered pH tiles had a small positive effect on early benthic colonisation in the tropics but this was later succeeded by similar species assemblages regardless of treatment. Thus, while it is worth considering the modification of concrete from an environmental/emissions standpoint, lowered pH may not be a suitable technique for enhancing biodiversity in the marine built environment.

KEY WORDS: Coastal defences · Concrete carbonation · Eco-engineering · Materials · pH · Biodiversity · Concrete

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Cite this article as: Hsiung AR, Tan WT, Loke LHL, Firth LB and others (2020) Little evidence that lowering the pH of concrete supports greater biodiversity on tropical and temperate seawalls. Mar Ecol Prog Ser 656:193-205.

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