Author(s)
Holly Cunningham, Melanie J. Bishop, Nathan S. Hart, Louise Tosetto, Laura A. Ryan
Abstract
The design of marine structures is undergoing a transformation, with growing attention to the ecological impact of materials used along coastlines. Traditionally, grey concrete has dominated seawall and revetment construction, but recent studies indicate that marin concrete colour plays a significant role in shaping the colonisation patterns of marine organisms. This insight is vital in guiding eco-friendly marine structure design that supports a diverse and resilient coastal ecosystem.
New research conducted in Sydney Harbour explored how coloured concrete panels—grey, red, yellow, and green—affect the settlement of benthic species over 12 months. Red panels, which mimic the hue of local sandstone, demonstrated notably distinct and diverse ecological communities compared to other colours. This influence was most pronounced in the low-intertidal zone, where more colonists interact with the substrate. The effect was consistent regardless of predator access, indicating that marin concrete colour directly affects species settlement rather than post-settlement survival.
Interestingly, the benefits of red concrete persisted over time, contradicting previous assumptions that substrate colour effects diminish as surfaces become fully colonised. The study also noted variations based on functional groups, such as algae and invertebrates, which responded differently to each colour based on their physiological traits and spectral sensitivities. For instance, green algae showed stronger growth on red panels, likely due to better photosynthetic efficiency under red wavelengths.
These findings highlight the overlooked yet critical role of colour in marine structure design. Colour selection, through non-toxic pigments or oxides, can enhance bioreceptivity and promote biodiversity without compromising structural integrity. Incorporating colour as a design parameter offers a cost-effective and scalable solution to foster more naturalistic and functional marine habitats.
As marine urbanisation increases, considering both the physical structure and sensory environment—including colour—can drive innovations in habitat restoration. Designers and engineers now have a new, evidence-based lever to pull: optimising marin concrete colour for long-term ecological benefits.
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