How Can Pesticides Affect the Development of Aquatic Life?

Source Article: Leandro et al., “Permissible concentration of mancozeb in Brazilian drinking water elicits oxidative stress and bioenergetic impairments in embryonic zebrafish.” Environment Pollution, volume 333, 2023, p. 122013,

Pesticides are widely used to provide better soil management, to control pests, and to avoid food waste in agriculture. However, these products can easily infiltrate water sources through natural processes, contaminating the aquatic environment and organisms that live in the aquatic system for a considerable amount of time until their degradation. Brazil, one of the most diverse and life-abundant countries due to the Amazon forest, has a large agricultural sector, one of the major sources of income for the country. As a result, its policies allow large amounts of pesticides in water sources. However, these high concentrations may cause toxic effects to water-living organisms, decreasing their survival and causing adverse effects.

With this in mind, researchers from Brazil collaborated to study the effect of the permissible concentration of the pesticide mancozeb, one of the most used pesticides in the country, in drinking water using the zebrafish model.

Wide plantation zone where a machine is spraying pesticides.
Agriculture uses large amounts of pesticides to keep food production unaffected. Image source: USEPA Photo by Eric Vance Byline, Public Domain, via Wikimedia Commons.
Zebrafish as a Model of Toxic Effects  

Zebrafish is a very versatile animal model and can be studied in various stages of life. Zebrafish embryos are particularly useful and can be observed during their whole development due to their transparent eggs, making it possible to easily evaluate the effects of chemicals such as mancozeb in their body and behavior.  

Since May 2021, the permissible concentration of mancozeb in drinking water in Brazil is 8 μg/L, but the previous amount of 180 μg/L was considered legal until 2021. In this study, after adding mancozeb in the water, both concentrations caused an impairment in embryo spontaneous movements, considered the first movement behavior of these animals. When this movement is impaired at both concentrations, zebrafish struggle to hatch from their eggs. Moreover, the concentration of 180 μg/L caused changes to body shape that could lead to permanent damage in the development of these animals. These results indicate that even Brazil’s legal concentrations of mancozeb are capable of triggering important physical damage in zebrafish embryos that may be caused by cell damage. 

High-contrast image where the main subject is a zebrafish, elegantly poised against a uniformly dark background.
Zebrafish is a versatile animal model to study environmental contamination by pollutants. Image source: Amatya Sharma, CC BY NC, via iNaturalist.
Agricultural Pollution Damages Cells

During development, there is a constant division of cells, and the organism’s normal functioning is essential to avoid future diseases or malformation. However, the exposition to pollutants can trigger the accumulation of reactive oxygen species (ROS), leading to inflammation and alterations in the cells’ mechanism. Without body’s normal function, cell components can be affected. The mitochondria, the most important energy source of living organisms, can suffer dysfunction and decrease their energy production.

In this study, the concentrations of 8 μg/L and 180 μg/L of mancozeb were responsible for reducing the energy production and energy efficiency of zebrafish embryos. These results show that the contamination causes limitations to the amount of energy that is dedicated to early life development, decreasing the chance of normal long-term survival of these animals. Moreover, it was shown that the amount of harm caused to zebrafish is directly related to the concentration of mancozeb in the water.

It is concerning that even the new legal limit for mancozeb in drinking water in Brazil causes mitochondrial dysfunction and oxidative stress in the zebrafish model, which indicates that is still not safe for aquatic animals and may cause developmental damage and inflammation diseases. 

How Does Aquatic Contamination Affect Us?

This study provides insights into potential long-term hazards for aquatic life but also makes us think about the combination of pesticides in the water. If only one chemical is capable of affecting aquatic life, how about the mix of many pesticides that end up in aquatic resources?

It’s also important to highlight that although the current concentration of mancozeb in Brazilian drinking water seems to be low (8 μg/L), the concentration allowed in the European Union, for example, is higher (24 μg/L), meaning that each country has its own politics related to water contamination. 

Globally, agriculture needs to be improved each day to allow our continued survival around the world. This study helps us to think about new guidelines and improvement of environmental legislation. We must turn to sustainable alternatives to pesticides in the future to avoid possible diseases and impacts in the aquatic biome.

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Renata de Mello

Renata de Mello

I'm a biologist and an MSc in Biochemistry who works as a lab technician at KU Leuven (Belgium). Outside the lab, I can be found reading fiction books, cooking Brazilian food, traveling across Europe, and working towards my passion for science and communication.

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