Biobased Electrically Conductive Hardening BioPaste for Underwater Coral Reef Restoration

Preserving coral reefs, essential ecosystems supporting 25% of marine species, is crucial as they face severe threats from climate change and human activities (1) . Thus, coral restoration, which involves cultivating corals and boosting their growth rate through micro-fragmentation (2) and electrochemically driven mineral accretion (3, 4) and then anchoring them onto reefs, is becoming essential for their survival. Standard anchoring methods include petroleum-based epoxy (5) or cement and cable ties (6), which are not sustainable and not efficient attachments. Hence, a sustainable conductive hardening bicomponent biopaste was manufactured to enhance coral attachment and transplantation onto different substrates including reef. Simultaneously, micro-fragmentation and electrochemical mineral accretion was realized using the biopaste on living corals to boost and combine different restoration strategies. The bicomponent paste is constituted of crosslinked vegetable oil, forming a biobased and biodegradable biopolymer matrix, and carbon nanofiller. Remarkably, the paste significantly hardens through mixing, transitioning from a compressive Young’s modulus of approximately 0.1 MPa to approx. 60 MPa and reaching strength similar to bricks (approx. 5 MPa). Through rheological tests, we demonstrated the tunability of the crosslinking dynamics of the paste by adjusting the relative quantities of the initiator and the accelerator. The pastes' resistivity was in the order of 10^-1 ohm m and their electrical properties were stable for over 40 days when immersed in seawater. Trials with living corals showed significant results (pvalue=0.01) at two weeks with test growth rates doubling those of the control group. Such a solution combines for the first time a controllable attaching method with micro fragmentation and electrochemically driven mineral accretion. It can offer versatility for application in aquariums and nurseries, does not require long-lasting metallic structures underwater, and could also be employed directly on the reef.
References:
1. Hoegh-Guldberg O, Pendleton L, Kaup A. Regional Studies in Marine Science. 2019;30.
2. Sutthacheep M. Ramkhamhaeng International Journal of Science and Technology. 2023.
3. Goreau TJF. Frontiers in Marine Science. 2022;9.
4. H. HW. Journal on oceanic engeneering. 1979.
5. Page CA, Muller EM, Vaughan DE. Ecological Engineering. 2018;123:86-94.
6. Unsworth JD, Hesley D, D'Alessandro M, Lirman D. Restoration Ecology. 2020;29.