By Niecole Killawee

The global population is expected to reach over 9 billion people by 2050 and the unprecedented number of humans to feed poses significant food security challenges. That's why Christopher Algar, an oceanographer at Dalhousie University, is working on technology to help with the sustainable development of the aquaculture industry so it can better meet a rising demand for seafood around the world.

His idea for an environmental remediation technique was the result of a collaborative meeting of the minds with Greg Wanger, a local microbiologist and founder of Oberland Agriscience in Halifax, Nova Scotia. In truth, the two were out for a beer when Wanger's background in microbial fuel cells and Algar's expertise in the geochemistry of sediments came together in a rough sketch on a napkin. After a few more serious iterations of their plan, the two scientists were ready to look for support from the OFI seed fund.

Christopher Algar (left) is pictured with co-op student Colin Ward in his lab at Dalhousie University
Image credit: Nick Pearce, Dalhousie University

"We had this idea, but we didn't really know if it would work," says Algar, an assistant professor in Dalhousie's Department of Oceanography. "The concept had potential and the seed fund gave us the money we needed to do an initial set of laboratory experiments to prove that it would work."

The proof-of-concept studies conducted in Algar's lab addressed a specific problem in aquaculture: the build-up of organic waste beneath fish farming pens. Fish feces, feed, and other forms of organic matter accumulate on the seabed, making it difficult for oxygen to reach down into the sediment below. It's a natural process that happens throughout marine environments but in aquaculture settings the sheer volume of fish living in a contained area expedites the build-up.

"That's a problem because when oxygen can't get in — if too much organic matter builds up — then microbes in the sediment use sulfate instead of oxygen," explains Algar.

Mud-loving microbes that turn to sulfate for their energy needs end up producing hydrogen sulfide, a toxic gas that can kill other organisms in the ecosystem. Consequently, environmental regulations pertaining to aquaculture tend to call for monitoring sediment sulphide levels in many jurisdictions. Marine environments with low water circulation make the problem worse, limiting fish farming sites to deep water or areas with lots of turbulence — areas that are often susceptible to storm damage, posing economic risks to the operation.

Algar and Wanger saw potential in the design and development of technology that addresses high sulfide levels at fish farms because, in addition to mitigating a key environmental problem, the aquaculture industry could then perhaps look to expanding operations into marine areas with calmer conditions. 

Their device is called a sediment microbial fuel cell and it connects two communities of microbes —one living in the sediment and the other in the water above — via an electrical circuit. The resulting flow of electrons between the two communities results in favourable chemical reactions at both ends and ultimately minimizes the amount of sulfide in the sediment. 

"It provides this metaphorical snorkel down into the sediment that essentially allows the [microbes'] metabolism to occur as if oxygen were there. It allows them to access, though not directly, the oxygen in the overlying water column," explains Algar.

Algar and Wanger's seed funding amounted to $28,800 and their project indeed showed promise as an innovative solution. It led to a paper in Nature: Scientific Reports and further financial support from the Innovacorp Early Stage Commercialization Fund. In addition, a spin-off company is currently in the works and next steps include collaborating with an aquaculture partner to test their sediment remediation technology in the field.

"The seed fund provides just enough to do that initial experiment on something that may be a little bit high risk," says Algar. "And it really was a seed that grew into even more funding.