by Dr. Julia M. Diaz, Nao Song, Dr. Sarah Allard, Scripps Institution of Oceanography, University of California San Diego
At the Scripps Institution of Oceanography at the University of California San Diego, the Diaz Lab is exploring how marine science can help answer research questions in soil and sustainability science. Across these systems, our work aims to reveal the potential uses of microbes, such as microalgae, for critical mineral recovery.
Microalgae are the invisible forest of the sea. Oftentimes algae are viewed in a negative light because harmful algal blooms caused by runoff can damage aquatic environments. However, the same ability that allows microalgae to overwhelm ecosystems is what makes them our planetary life support system: marine microalgae generate half the oxygen we breathe. It is also what makes these microorganisms interesting from a phosphorus sustainability standpoint, because algae can quickly take up and store phosphorus from water.
One way that algae store phosphorus is by forming inorganic polyphosphate, a polymer of orthophosphate. This same polymer is currently being marketed as a slow-release source of phosphorus in some fertilizers, while it is also involved in technologies for biologically removing phosphorus from wastewater. Because of the need for sustainable supplies of phosphorus, we are investigating how to more fully tap the potential of polyphosphate-bearing microbes, such as algae or bacteria, to help meet this demand.
Recently, we have launched pilot projects in collaboration with growers in the San Pasqual Valley Agricultural Preserve in San Diego County. In one project, we aim to assess whether polyphosphate-bearing microalgae can act as a natural slow-release source of plant-available phosphorus. In another, we are working with Jeff Bowman’s microbial ecology group at Scripps Oceanography to reveal the genetic basis of phosphorus release from soils with a long-term history of fertilization using organic inputs.
By collaborating with agricultural centers such as the San Pasqual Valley Agricultural Preserve, we hope that our findings can ultimately inform the way phosphorus is managed. The Diaz lab is part of the UC San Diego Soil Health Center, which takes an interdisciplinary approach to understand the biological, chemical, and physical factors that influence soil health, as well as the social, economic, and policy landscapes that underpin adoption of innovations in soil health management. Our work with the UC San Diego Soil Health Center shows how university scientists can carry out research in collaboration with local growers, developing and testing innovative solutions to pressing challenges in a community-centric way.
At the national level, representatives of the Diaz lab help shape policies around phosphorus sustainability. As an AAAS Science and Technology Policy Fellow at the U.S. Department of Energy from 2023–2025, Professor Julia Diaz contributed to interagency policies and reports concerning the emerging bioeconomy. As phosphorus-dependent energy technologies develop, such as biofuels and lithium iron phosphate batteries, these technologies may compete with the use of phosphorus in food production. In recognition of these competing uses, and in a manner consistent with the addition of phosphate to the national critical minerals list, we believe that phosphate should be included in DOE’s 2026 Critical Minerals Assessment.
Opinions expressed here do not necessarily reflect those of the Sustainable Phosphorus Alliance or its members.