A research team from the Department of Chemical Engineering at the University of Almería (UAL) and the Solar Energy Research Center CIESOL has demonstrated the bio-stimulating effect of the microalgae ‘Scenedesmus almeriensis’, cultivated in both freshwater and seawater, on the development and growth of ornamental plants, specifically geraniums.
In contrast to traditional fertilizers, bio-stimulants do not directly provide nutrients but optimize the way the plant absorbs and utilizes them. The results of the study, funded through two projects from the Ministry of University, Research and Innovation, RE USE and BLUE FUTURE, and a third from the Ministry of Science, Innovation and Universities, demonstrated that the biomass extracted from this microalgae can enhance growth, flowering, and, ultimately, the overall health of crops.
Although there are differences depending on the type of water in which it is produced, in both cases, it increased resistance to stress, whether from water salinity, drought, or the extreme temperatures typical of Almería. This advancement can reduce dependence on chemical fertilizers and optimize water usage in agriculture.
The ‘Scenedesmus almeriensis’ is a native freshwater microalgae of Almería, discovered in 2005. It had grown in wastewater, but it was the first time its cultivation in marine environments had been explored. «Although the bio-stimulating potential of this strain had been demonstrated, we wanted to see how its properties change when produced in seawater, with the aim of reducing water consumption and improving sustainability,» explains UAL researcher Tomás Lafarga, one of the study’s authors, to the Descubre Foundation, an organization under the Ministry of University, Research and Innovation.
Differences between freshwater and seawater cultivation
The initial part of the work, which also involved researchers from the National University of Agriculture (UNAG) in Honduras, aimed to observe how ‘Scenedesmus almeriensis’ adapts its composition, growth rate, and even morphology in response to saline stress.
‘Scenedesmus almeriensis’, native microalgae of Almería.
Thus, although the microalgae adapts to seawater, its growth rate decreases. They also observed a larger size and rounder shape compared to the strain cultivated in freshwater. Additionally, the biomass has a lower protein content, but enough to generate a positive effect on plants.
The decrease in productivity is offset by an increase in sustainability and process viability. «Cultivating in seawater reduces consumption in production by over 90%. It also reduces the risk of contaminant parasites. And all of this without compromising the stimulating capacity of the microalgae,» highlights Lafarga.
Evaluation of the bio-stimulating effect
To assess the properties of the biomass, researchers conducted trials with strains cultivated in freshwater and seawater, both in the lab and under real conditions in a greenhouse, the results of which are detailed in the study titled ‘Biostimulant effect of a novel seawater-adapted strain of Scenedesmus almeriensis on garden geranium’, published in the journal Algal Research.
In laboratory tests, extracts from both microalgae improved watercress seed germination by up to 30% compared to watering with just water. Furthermore, they stimulated root formation in soybean seedlings by up to 300%, although the freshwater-produced strain showed superior stimulating capacity.
The results were validated in a greenhouse with geraniums. After 70 days of monitoring, significant improvements were recorded in plant height and diameter, in root growth, as well as in the number of leaves and flowers, especially in those treated with freshwater.
Research team that has demonstrated the bio-stimulating effect of this microalgae.
The research shows that greater development can be achieved with less water and nutrients. «By obtaining stronger plants, they will be better able to withstand the effects of climate change or water salinity, which is increasing in Almería due to seawater seeping into aquifers,» clarifies the UAL chemical engineer.
This study opens up new possibilities in the use of this growth-enhancing compound in agriculture. ‘Scenedesmus almeriensis’ could be a sustainable alternative to chemical fertilizers, helping to reduce the environmental impact of this sector. Moreover, production in seawater could minimize the consumption of an increasingly limited resource,» emphasizes Lafarga.
The next steps of the research include optimizing the application for better results, as well as the potential to consistently produce the seawater strain throughout the year. They will also explore its application in other crops, following cucumbers and zucchini, which will be tested this spring.