Last semester, we introduced Sofía Velázquez Sierra, our 2024 Seed Fund recipient, and we are so excited to present a final update on the results obtained in her research! Read on to learn more about what she uncovered and what follows next.
Her study, titled Flowing Towards Restoration: Cissus verticillata Phytoremediation Potential for Juan Mendez Creek Restoration in San Juan, Puerto Rico, investigated the potential of the possum grapevine (Cissus verticillata) to eliminate heavy metals from the water at the creek located in the Northern region of our island. This process is known as phytoremediation, in which certain plant species can absorb pollutants in their tissues and effectively eliminate them from the soil or water. Sofía’s goal was to investigate if this particular vine species, native to Puerto Rico, could remove heavy metals (specifically cadmium and lead) from our waters. If so, then perhaps we can consider this non-invasive and cost-efficient process as a method to improve water quality in our local watersheds.
In August 2024, Sofía collected water and plant samples from the Juan Méndez Creek (JMC) and developed an experimental design that would be carried out over the following weeks in a laboratory at the University of Puerto Rico at Río Piedras. The water samples underwent quality assessments to establish baseline parameters of nitrogen, phosphorus, heavy metals, and the bacteria Enterococcus. Then a total of 25 samples of possum grapevine were collected, each one standardized by initial shoot numbers and total biomass, which were placed inside a controlled-climate chamber with light, humidity, and temperature conditions similar to those at JMC, allowing the observation of growth in this controlled environment.
After weekly monitoring, results revealed varying removal efficiencies for cadmium and lead, with a notably higher efficiency for lead, reaching 80.13%, compared to 44.33% for cadmium. Interestingly enough, translocation factor analysis revealed an inverse pattern, with the possum grapevine exhibiting a higher translocation factor for cadmium than for lead. In addition, all samples displayed remarkable adaptive capacity in all containers, evidenced in the growth of 38 new leaves across all individual plants studied, suggesting physiological resilience under heavy metal stress. As a reaction to exposure, this vine acts as a lead excluder by immobilizing the metal in the root zone while serving as a cadmium accumulator by translocating it throughout the plant’s tissues.
So, what does this mean?
These findings underscore the potential of the possum grapevine as a non-invasive instrument to decontaminate local watersheds affected by heavy metal pollution.
“Further research should focus on extending the treatment period to determine whether a saturation point exists for the possum grapevine, beyond which no additional absorption occurs. This would offer valuable insight for developing a strategy to incorporate this vine into real-world restoration efforts.” — Sofía Velázquez
What’s next?
Our Seed Fund recipient is currently working on completing the manuscript and preparing presentations to share the knowledge obtained with organizations and individuals working in restoration to develop a comprehensive strategy for incorporating this vine into real-world restoration efforts. She also proposes exploring other widely available native vines that may demonstrate even greater phytoremediation potential, further suggesting that the presence of these additional species could explain why heavy metal levels at the Juan Méndez Creek were below detection limits.
We want to thank everyone who donated to our Seed Fund Program! With your support, Sofía’s “ridges to reefs” research was made possible and we congratulate her on the success!!
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