The Cerrón Grande reservoir is the largest water body in El Salvador and is home to over fifteen species of fish and a wide variety of submerged and floating flora. Due to its international importance in conserving biological diversity, this wetland received the Ramsar (short for the Ramsar Convention on Wetlands of International Importance Especially as Waterfowl Habitat) designation in 2005.
Although the reservoir was constructed between 1973 and 1976 to produce electricity, the natural wealth found in its 135 km2 provides water and food for the sustenance of local communities, allowing the commercialization of products derived from artisanal fishing, shell-fishing, and hunting. This is particularly important in 2022, the International Year of Artisanal Fisheries and Aquaculture.
Despite its great relevance, though, the reservoir is currently threatened by the accumulation of solid waste, erosion, eutrophication, pollution, and the presence of invasive species. To mitigate these environmental issues, a multidisciplinary group of scientists from the “José Simeón Cañas” Central American University, a member institution of the United Nations Academic Impact (UNAI) in El Salvador, stepped in.
The research group, led by Dr. María Dolores Rovira, is conducting a comprehensive study to understand the eutrophication processes, identify invasive species and their potential uses in commercial applications, and measure pollution levels. It started the project in 2016, and the national government has supported it through the Ministry of Environment and Natural Resources, as well as international stakeholders.
In the first phase, the group quantified the biomass in the reservoir during the dry and rainy seasons due to the high pollution levels. Accordingly, the group classified this contamination indicator as the mass of invasive vegetal species and phytoplankton blooms. As a result, the common water hyacinth (Eichhornia crassipes) was identified as the predominant invasive species, and several phytoplankton species were detected in the water.
The water hyacinth, native to South America, is a cause of concern considering its disproportionated growth tendencies in lakes, slow-moving rivers, and swamps. In Cerrón Grande, the results of this first phase also showed that the hyacinth covers up to 30% of the water surface in the rainy season, hindering artisanal fishing and deteriorating the water quality and balance of the ecosystem.
These findings motivated a second phase of the project focused on identifying applications in which the hyacinth may be used as fuel or raw material for generating new value-added products. It turns out that it satisfies all the criteria for bioenergy production. These criteria include a high content of cellulose, low content of lignin, high degradability, resistance to pests and diseases, no occupation of land, and the potential to become a solid or gaseous fuel.
Despite all these attributes, the main drawback to using water hyacinth as an energy source is its high moisture content. To solve this problem, the research group studied a natural drying process and the influence that different types of plant cuts can have on moisture content. The experimental procedure involved collecting hyacinth samples from Cerrón Grande and obtaining their drying curves.
Laboratory analysis done by the research group showed that natural convection reduces the moisture content to acceptable levels. Based on this result, the group also developed a methodology so that this process can be carried out handcrafted by locals and determined that the hyacinth has a calorific value comparable to the characteristics of other biomasses widely used as fuels in many industrial processes.
Similarly, the research group found that hyacinth can be used to produce construction materials with properties similar to compressed wood. However, besides water hyacinth, the results of the first phase also showed a high presence of phytoplankton and algae. Thus, the latest efforts of the researchers have been focused on determining the species of algae that proliferate in Cerrón Grande.
High pollution levels also cause the proliferation of algae in the reservoir since it provides too many nutrients that facilitate the growth of microorganisms. This is known as eutrophication and causes the deterioration of the water quality, depletion of dissolved oxygen, sludge generation, unpleasant odors, and death of aquatic species. Results of this third phase have determined that the predominant species of algae are cyanobacteria.
In addition, the researchers found some species that may generate toxins, which can be highly harmful. For example, José Luis Sierra, a biologist that is also part of the group, said that “fairly intense proliferation of cyanobacteria develops in Cerrón Grande and about 99% of the cell abundance corresponds to a potential producer of microcystin, which is a toxin regulated by the World Health Organization for water subjected to human applications”.
According to Dr. Rovira, the research group leader, “all the biodiversity and economic activities that depend on the Cerrón Grande may be lost if the environmental conditions in the reservoir continue to deteriorate.” Therefore, the expert explained, constant monitoring is fundamental, and it is required concerning “not only the current state and changes of its water quality but also the presence of invasive species.”
This is crucial, says Dr. Rovira, for decision-makers and stakeholders involved in managing this essential natural resource in El Salvador”. In the future, she expects the group sets up a remote sensing system for monitoring Cerrón Grande, using satellite images without sampling at the site. Implementing this system would facilitate permanent measurement of the reservoir’s water quality and assessment of the presence of toxins.
The project conducted by this UNAI member institution in El Salvador is a concrete example of impactful research to advance the 2030 Agenda for Sustainable Development and, in particular, the Goals related to environmental protection. Furthermore, the contribution of universities and colleges worldwide demonstrates their commitment to a healthier planet through their knowledge and expertise.
