Marine engineering projects like cross-sea bridges and port dock banks, crucial for exploring and utilizing the sea, face a daily challenge: erosion by sea water.

Traditional anti-erosion paint has a strong odor and could pose a threat to the ecosystem. A research team from the College of Aerospace and Civil Engineering, Harbin Engineering University (HEU), figured out a unique solution: Let oysters do the trick.

Oysters stand out

According to Lv Jianfu, HEU professor and the team lead, marine sessile organisms can be used to prevent erosion, meeting not only the requirements of engineering construction, but also restoring the ecosystem.

The first step in adopting this method was to pick the right species. Lv and his team cooperated with other research institutions, including the Institute of Oceanology, Chinese Academy of Sciences, to conduct field research and sea tests. Many sessile organisms were compared and screened, and oysters stood out.

Oyster reefs, formed by clusters of oysters growing in a fixed position, are known as "ecosystem engineers." They possess multiple ecological uses such as improving the water quality, enhancing biodiversity, and protecting coastlines.

Lv's team reconstructed the design logic of marine infrastructure by deeply integrating cement-based materials and marine organisms, pioneering the world's first integrated technology for high-durability marine concrete engineering and ecological restoration based on oysters.

This technology creates a biological armor for marine engineering projects, which is highly anti-corrosive, low cost and self-restorative.

By activating the natural power of marine sessile organisms like oysters, the life of engineering projects such as piers and cross-bridges can be extended to more than 50 years.

Attracting and settling oysters

Research shows that the biological armor would leverage its protective capabilities fully only when marine sessile organisms cover more than 95 percent of the surface of the concrete works. Therefore, how to attract oyster clusters to voluntarily come to the targeted area and build a defense system became another key issue.

Lv's team designed a full-chain solution, which included artificial induction, material design and function integration, greatly enhancing the safety and durability of the concrete works.

Considering the sophisticated marine environment, Lv's team conducted tests at different marine engineer works, including cross-sea bridges and port wharfs in the Yellow Sea, the East China Sea and the South China Sea.

They developed a specific oyster inducer based on the adhesive properties of dominant oyster species in specific sea areas and their environmental features. Coupled with biological concrete, cement-based paint and oyster adhesive bases, this inducer quickly attracted a large number of oysters.

The team also developed a comfortable home for oyster larvae to grow in by controlling the penetration rate of materials, innovatively created from industrial and agricultural solid waste like fly ash and slag.

This approach transformed negative defense into active defense by sessile organisms.

Ecological added value

This new technology, recognized by experts as groundbreaking, provides ecological added value besides engineering work protection.

The biological concrete, cement-based paint and adhesive bases have double advantage: They are both highly efficient in erosion prevention and ecological restoration. Especially, the cement-based paint doesn't emit any volatile organic compound, realizing the leap from low carbon to negative carbon.

In addition, the filter-feeding function of oysters can purify the water, enhance fishery resources and boost biodiversity. In the long term, it also has the potential for net carbon sequestration.

According to Lv, the oyster-like reefs formed on the surface of engineering works can filter approximately 100 tonnes of seawater per square meter every day, significantly reducing suspended particulate matter and eutrophication levels in the water body.

The three-dimensional structure of these reefs provides an excellent habitat for marine organisms. Not only are they fish spawning grounds and crab shelters, they can also reduce wave energy and coastline erosion.

Incorporating anti-erosion for marine engineering projects, ecological restoration and aquaculture, this technology provides a solution for the development of green marine technologies.