The ocean is under tremendous pressure. In Northern California, 95% of its ~250km kelp forest has been lost due to sea urchin overgrazing on the kelp. The sea urchin population skyrocketed to 60x its average due to a disease-driven death of its main predator and their ability to survive acidifying ocean conditions. Harvesting as a mitigation strategy has produced hundreds of tons of urchins that have primarily ended up as compost.
What if the sea urchin harvested to protect kelp forests could be leveraged to support local marine ecosystems?
Second image is an AI-generated render demonstrating the intertidal deployment, ability for individual blocks to be configured into modules, and the settlement of oysters.
Urchinode is both a material and a proposal for a new material system that investigates how this sea urchin waste can be transformed for productive use within the ocean, rather than just being removed from it.
Through material-driven design research, this project develops a biodegradable composite that serves as a foundational substrate for oyster reef settlement.
Its calcium carbonate composition attracts marine larvae and its ability to be cast into high-surface area forms further enhances its settlement potential.
While oyster shells or oyster-shell integrated biocomposites/concretes have typically been used for oyster reef settlement, the limited supply of oyster shells has bottlenecked the scalability of various projects and pushed scientists to seek alternate substrates. In fact, this is the case for an existing oyster reef project located just 250km down the coastline from existing Northern California sea urchin harvest sites.
Urchinode seeks to fill this gap by leveraging sea urchin as a local, abundant, and calcium-carbonate rich aggregate for the substrate. By casting the biocomposite into fabricated molds, the material hardens into structural blocks that oysters can settle and grow on. As oysters self-cement over time, the biocomposite degrades such that no waste is left behind.
Demonstrating the scale of a single Urchinode block. In true deployment, multiple would be placed together to form a module.
Beyond material composition, in designing the blocks, Urchinode considered both the ecological and economic impacts of their design. From an ecological standpoint, the hexagonal design allows blocks to tessellate together and stack to meet location-specific depths or project-specific spacing/scaling that aligns with best practices from existing research. The surface texture imprinted on the faces of the blocks aims to provide microhabitats for larvae settlement and to reduce water velocity near the block’s surface which has been shown to aid larvae settlement and growth. From an economic standpoint, the size of an individual block is able to be carried by an adult and therefore does not require specialized equipment to deploy.
Urchinode applies this sea urchin biocomposite as a temporary scaffold for oyster settlement and growth. Leveraging existing proof points of this temporary approach, this strategy eliminates waste behind or future infrastructure retrieval costs. This is particularly relevant when considering the financial constraints of large-scale marine projects.
The project combined literature review, hands-on experimentation, and testing to assess the viability of the hypothesis that sea urchin could be used as a substrate in oyster reef settlement. Through various trials, various aggregate-to-binder ratios, binders, curing methods, and aggregate ratios were experimented with to understand their influence on the material’s surface texture, rigidity vs flexibility, and durability to water submersion.
Urchinode highlights an opportunity for waste valorization as a restoration strategy that can connect distributed projects within a given region.
Laser cutting deployment map for final exhibition.
The project validated the ability for a biofilm (which promotes oyster settlement) to grow on the material as well as its ability to withstand prolonged submersion in water. However, the settlement rate of oysters and degradation rate of the material need to be quantified to further refine the material composition.
As the first project to propose sea urchin as the primary calcium-carbonate source for an oyster reef substrate, Urchinode contributes new knowledge to the fields of regenerative design, nature-based solutions, and bio-based materials.
I look forward to the opportunity to collaborate with others in this field to further develop the material’s potential.
