A team of scientists identified a tiny native fish from South America as an effective sensor for the detection of hydrocarbons in water sources. The species is Cnesterodon decemmaculatus, better known as the “water mother” or “stream fish” and is abundant in rivers in Argentina, Uruguay, Paraguay and southern Brazil.
Just as the liver is responsible for filtering certain toxins in the human body, this fish has enzymes that are activated by the presence of hydrocarbons in the water. Scientists from the National Scientific and Technical Research Council (Conicet), led by Gabriela Rabuffetti, propose this fish as an effective biomarker in a study published in the scientific journal Science of the Total Environment.
A South American fish to detect hydrocarbons
A team of researchers found that watercress has high activity of the enzyme EROD (ethoxyresorufin-O-deethylase) when exposed to hydrocarbons. This enzyme, found in fish tissues, is a biological indicator of these contaminants.
Pedro Carriquiriborde, co-author of the study, explained in a Conicet statement that EROD activity was analyzed in adult and juvenile fish, both in the laboratory and in their natural environment. It was observed in the tests that enzyme levels increased significantly in the liver, gills and fish muscle exposed to these toxic compounds.
Cnesterodon decemmaculatus fish are highly tolerant to contaminants. Photo: Conicet
Similarly, women were found to present a more pronounced response. “Of all individuals, females are the ones that show higher levels, but this is related to their larger size,” commented Rabuffetti for the above article.
The fish, which is viviparous, also showed a disturbing effect: the transfer of contaminants from the mother to the embryos. This makes mother water a an effective model for studying the intergenerational transfer of pollutants. Furthermore, fish chronically exposed to hydrocarbons did not develop resistance to the enzyme, meaning that EROD remains active as long as exposure to the compounds continues.
Great potential for environmental monitoring
The use of water strain as a biomarker has great potential in environmental monitoring. Until now, EROD enzyme activity has been used in other countries as an indicator of hydrocarbon contamination in animals, but this is the first study to confirm its effectiveness in species native to South America.
Gabriela Rabuffetti emphasizes that the EROD enzyme is able to detect the presence of hydrocarbons before the effects on organisms are irreversible. These types of biomarkers complements traditional chemical measurementswhich detect contaminants in water but do not offer information on biological effects on living beings.
The team performed various tests to evaluate the rate at which the enzymes reacted to the hydrocarbons. Photo: Conicet
The study revealed that fish living in contaminated waters around the La Plata Petrochemical Pole showed elevated levels of EROD compared to fish living in cleaner environments such as Espinillo Creek, a more protected location. This confirms it the water mother can act as a guardian speciesfacilitating the monitoring of water bodies contaminated with hydrocarbons.
The ability of this fish to continue to respond to contaminants without developing tolerance makes it an essential tool for early detection of contamination to help prevent irreversible damage to aquatic ecosystems.
What type of hydrocarbons can mother water detect most effectively?
Mother Water is particularly effective in revealing polycyclic aromatic hydrocarbons (PAHs) through EROD enzyme activity. These compounds are known for their toxic and carcinogenic potential and are common in environmental pollutants such as those from the incomplete combustion of fossil fuels and oil spills. Some of these are: benzene, naphthalene, anthracene, fluorene and pyrene.
