Biocontrol experiment in circulating ponds built by C. Rakowski at Brackenridge Field Lab. Photo by S. Duchicela (2021)

Applications to algae cultivation

Algae cultivation, especially phytoplankton cultivation, is the basis of a promising class of environmental technologies. These emerging technologies harness the high productivity and affinity for polluting nutrients that characterize these microscopic plants, to achieve various useful ends. For example, phytoplankton can be cultivated in wastewater so they clean the wastewater as they grow, and then the phytoplankton biomass can be harvested for use as a fertilizer or biofuel. However, one reason these technologies are not yet widely adopted is the inevitable intrusion of zooplankton which consume the phytoplankton.

I am investigating potential methods for biological zooplankton control in the circulating ponds where phytoplankton is cultivated. Biological control is preferable to chemical control as it can be cheaper — a manager can establish predator populations once rather than requiring indefinite repeated chemical treatments — and it does not cause pollution. As multiple zooplankton species of vastly different sizes normally colonize these ponds, I am centering my approach on using multiple predator species varying in size, including insects and fish. I am also testing ways to reduce intraguild predation, essentially to prevent the fish from eating all the insect predators, to encourage these various predators to coexist and therefore keep the various zooplankton under control simultaneously. Consistent zooplankton control should encourage consistently fast algal growth and therefore consistently high performance of the target metrics (e.g. wastewater cleanup and biofertilizer production).

Chase Rakowski
PhD Candidate