A team of students, known as the Urchin Merchants,from the Department of Mechanical Engineering at the University of Colorado Boulder has designed and built a large underwater vacuum for collecting purple sea urchins, which pose a significant threat to bull kelp forests along California’s coastline.
Since 2014, 95 per cent of bull kelp beds off the coast of California have died as the population of purple sea urchins, which feed on the kelp, has grown by 10,000 per cent.
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‘Our project is really aimed at collecting large amounts of those urchins and improving the collection rates of divers, which is not possible with the current methodology,’ said Josh Ayers, the Urchin Merchants’ systems and testing engineer.
Researchers estimate that using current techniques, it will take 15–20 years to clear the urchin barrens. However, the Urchin Merchants’ specialised suction device could increase collection rates by six times, bringing that 20-year timeframe down to less than five years in a single location.
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‘We knew we wanted to save the kelp forests and we figured the best way to do that would be removing purple sea urchins rather than planting kelp,’ said Project Manager Dorothea French. ‘We thought we might try to build an autonomous, underwater robot, but that would take 10–15 years and we need a solution now.’
The four-metre-tall prototype features a large tube at the top that serves as a sorting system. The tube shuffles larger urchins to one side and smaller urchins to another. Any non-urchin material, such as small animals or sand, moves straight out the top. On the other end of the vacuum is a flexible hose that divers can use to suck up urchins from the ocean floor.
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The team used insights provided by conservation organizations and professional divers to hone their designs. In particular, the divers wanted a system that was both easy to use and inexpensive.
‘The vacuum uses a highly efficient air lift pump that is able to collect large quantities of small objects from the ocean floor,’ said Zach Sorscher, the team’s CAD engineer. ‘Think of it as a super tool that we would give to a diver to accompany them on their dives to improve collection rates.’
The team built the prototype as part of their capstone project in the department’s Senior Design course and are now testing the vacuum. They hope that it will prove useful not only in California but in other parts of the world in which booming urchin populations are devastating kelp forests.
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‘We just want to design and build a project that could help the world,’ said the team’s logistics manager, Heather Hunt. ‘We are using our engineering expertise to make a difference.’