Engineered structures like dikes and other coastal defenses are used to prevent erosion and mitigate storm impacts. Unfortunately, these solutions often fail to safeguard the ecological functions of the coastal areas they aim to protect.
A recent study published in 'Biointerphases', an AVS journal by AIP Publishing, highlights an innovative approach developed by researchers from Southeast University and the University of Chinese Academy of Science. The study explores the use of advanced cement materials to promote the ecological health of coastlines.
"New substrate materials need to be developed to reduce the biological toxicity effects on marine organisms," explained Xiaolin Lu, one of the study's authors.
Current artificial reef structures typically utilize cement with a high alkalinity (pH +12), which can harm biofilm-a layer of microorganisms essential for marine life. This biofilm supports coral and other marine organisms by providing a food source and promoting larval settlement.
To address this issue, the researchers tested a new cement-based substrate designed to be less harmful to marine ecosystems. Starting with a limestone and clay base that sets underwater, the team incorporated two treatments: polyacrylamide, a synthetic resin used in water treatment, and chitosan, a biopolymer derived from crustacean shells. These materials were either mixed into the cement or applied as a surface coating to enhance its ecological properties.
The treated and untreated samples were then tested in a sea tank environment to measure mechanical strength, biofilm growth, and coral health. Results showed that the surface-treated samples exhibited the most biofilm growth after two days, with continued improvement over 30 days. Coral samples also demonstrated better survival and growth on these treated surfaces compared to untreated cement.
While bulk-treated samples supported less biofilm and coral growth, their mechanical properties were notably weaker compared to untreated cement and surface-treated samples. Despite these limitations, the surface treatments showed promising biocompatibility for promoting marine organism growth without compromising the substrate's long-term durability.
"These new treatments showed the necessary biocompatibility in a simulated marine eco-environment, which can be used to promote biofilm growth without interfering in extended habitation of model coral samples," said Lu.
The team plans to extend their research by testing the long-term wear and biocompatibility of the treated cement in real-world marine environments.
Research Report:A phenomenological investigation of organic modified cements as biocompatible substrates interfacing model marine organisms
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