Among the labs of Brazil’s National Institute of Amazonian Research, or INPA, is what’s known as the “room of the future.” Here, an extreme climate change scenario is being simulated according to projections by the United Nations’ Intergovernmental Panel on Climate Change (IPCC). The temperature is around 5° Celsius (9° Fahrenheit) hotter than the average for Manaus, capital of the state of Amazonas and the largest city in the Brazilian Amazon, and atmospheric CO2 level is higher, at 708 parts per million, than the around 420 ppm level of today.
In this room of the future, biologist Samara Souza has carried out an experiment with tambaqui (Colossoma macropomum), exposing these Amazonian freshwater fish not only to these climatic extremes but also to a mix of pesticides that have been found in the rivers and lakes around Manaus.
“With climate change, increasing temperatures are not the only factor we need to pay attention to,” says Adalberto Val, coordinator of INPA’s Adapta program, which studies how the Amazon’s aquatic life is coping with climate change. “We should also evaluate the ways in which the temperature and carbon dioxide concentration in the atmosphere interact with other degrading factors in the environment like pesticides, forming dangerous synergies.”
Souza is a specialist in the effects of contaminants on Amazonian fish, and already had a solid understanding of the ways in which different pesticides affect the animals. Combining these with an extreme climate change scenario is, for her, one way to gain a better understanding of what occurs inside habitats as well as what challenges organisms will face in the future if the issues aren’t dealt with by public policy.
“However, it’s impossible to recreate everything that happens in the environment inside a laboratory,” Souza says. “It’s possible that the interactions and effects we saw in our experiments are even more negative in nature.”
In her study, Souza subjected 36 young tambaquis to one of two different scenarios: one simulating current temperature and CO2 levels, and another simulating the extreme scenario. The animals were exposed to these environments for 96 hours. They were also exposed to a cocktail of four agrochemicals typically found in the region: the pesticides chlorpyrifos and malathion, the herbicide atrazine, and the fungicide carbendazim. These were into the water at concentrations similar to those found in the bodies of water around Manaus.
Yet even at these concentrations, lower than those considered lethal to the fish, the mix of compounds had negative effects on the tambaqui, including liver damage and negative impacts on the nervous system, leading to paralysis and loss of function. However, when the extreme climate scenario was added to the mix, some of these impacts worsened. In other words, at higher temperatures and CO2 levels, the fish lose their capacity to metabolize and expel these compounds from their bodies.
This happens because such high temperatures in the environment require the fish to adjust their metabolism rate. The consequences of this process are serious. For example, contamination by organophosphate insecticides leads to the inhibition of acetylcholinesterase (AChE), an enzyme crucial for the propagation of nerve impulses in the fish, together with other enzymes that have an antioxidant action on the gills.
“When put in contact with the contaminated water, the fish who were already dealing with high temperature and higher CO2 concentrations were more susceptible to the agrotoxins because their metabolisms were not prepared to respond to them,” Souza says. “This produces more damaging effects than in today’s climate scenario.”
The combination resulted in irreparable damage to the animals’ livers and to their blood cell DNA. “The results showed that a future of climate change combined with pesticides will be harmful to the fish in the Amazon, possibly leading to the loss of biodiversity,” Souza says.
The effects of agrotoxins on fish
According to data from Brazil’s Ministry of Agriculture, Livestock and Food Supply (MAPA), there are 4,455 agrotoxins approved for agricultural use in the country today, with diverse uses and formulations ranging from crop farming to pasture. Of these, 1,017 are organophosphate insecticides like chlorpyrifos and malathion, the compounds used in the tambaqui study.
A number of studies have sought to understand the effects of organophosphates on aquatic organisms because of the way in which these compounds act. These chemicals disturb nervous impulse function control in the insects they’re designed to eradicate, inhibiting the production of the AChE enzyme. “This creates a short in the nervous system, leading to muscular paralysis and insect death,” says Roberto Artoni, a biologist and geneticist at the Federal University of São Carlos, in São Paulo state.
But the compound doesn’t only affect the pests it targets. These organophosphates have the same effect on fish and aquatic insects when they come into contact with bodies of water. Artoni has also authored studies that test these effects on tambaquis, mostly using another readily accessible organophosphate on the market, trichlorfon. “This compound causes fish to lose their balance. Depending on the concentration, the animal begins swimming on its side, becoming too lethargic to escape from predators or move around in their natural habitats,” he says. “Very few fish survive when exposed to a concentration that is 50% of the levels considered lethal.”
When analyzing liver tissue from the tambaquis, Artoni and his team also found that trichlorfon leads to cellular death, activating genes related to tumor formation. “If we use the tambaqui as a model, we can presume that, in the environment, these compounds will also harm the health of other fish or even the aquatic insects who compose part of the rivers’ food chains. Finally, these agrochemicals may reach humans as they build up in the fishes’ muscles, which would lead to equally relevant health-related consequences,” Artoni says.
How agrotoxins reach Amazonian rivers
In December 2019, Spanish ecotoxicologist Andreu Rico visited the Brazilian Amazon to evaluate agrochemical levels in the bodies of water in the cities of Manaus, Belém, Santarém and Macapá. It was Rico’s research that led Samara Souza to establish the realistic levels of compound concentrations she should use in her research with the tambaquis.
Rico carried out an evaluation of the toxic capacity of these components in the Amazon based on existing data on lethality levels of the compounds for different species. The data made it possible to determine that concentrations of chlorpyrifos and malathion insecticides found in the rivers surrounding these cities are highly dangerous for aquatic biodiversity. Eleven compounds in all were found in the water.
“However, we used species that had already been studied in the literature as references because there were not sufficient data to evaluate the specific risk for Amazonian species,” Rico says. “Among the agrotoxins we tested, we found no significant difference in sensitivity between Amazonian fish and fish from other regions.”
Population growth in Amazonian cities like Manaus has led to increased demand for food, which is now being met by small farms surrounding these metropolitan areas. According to data from the multidiscipline mapping collective MapBiomas, land area dedicated to farming on the outskirts of Manaus surged from 16 hectares in 2004 to 197 hectares in 2022 (40 to 487 acres).
A 2013 study showed how the cultivation of nonnative fruits and vegetables is responsible for a jump in the use of agrotoxins to fight pests and competition from other plants. Once in the soil, the chemicals leach out and soon enter the rivers.
But studies on pesticide use in the region have been carried out exclusively by universities and research centers, with no official government monitoring of its growing use. The lack of data hides, in fact, many other uses of these compounds going uncontrolled or unmonitored in the region.
Ana Gomes, a professor of parasitology at the Federal University of Amazonas, in Manaus, cites the case of trichlorfon being used to combat parasites at fish farms in the local aquaculture community. “Since there are no controls for the use of this agrochemical on aquatic animals, it is being used illegally in aquaculture. There is also no initiative on the part of government agencies in the region to monitor the use of these products in aquaculture,” Gomes says.
Studies by Artoni and others highlight how the negative effects from agrotoxin exposure that they found in lab tests have been replicated at fish farms in the region. The studies show that organophosphates can remain in the entrails of exposed animals for up to 15 days. And with no controls on fish farms releasing their water back into natural waterways, “the possibility of these compounds reaching the rivers is very likely,” Gomes says.
Reached for comment by Mongabay, the Amazonas Independent Aquaculture Association denied the use of the cited compounds by fish farmers in the state. The association hasn’t carried out any formal evaluation into the issue.
Agrochemical use in Brazil and alternatives
“The growing agricultural sector in Brazil explains just one part of Brazil’s agrochemical consumption,” says biologist Charles dos Santos. In 2018, he published a study that ranked Brazil as the world’s top user of agricultural pesticides, following a 150% growth in demand over 15 years.
While this increase is directly related to the expansion of Brazil’s agricultural frontier, dos Santos points to the indiscriminate use of these compounds as another significant factor. “There is a tendency to use much larger quantities than those recommended because of the fear of losing crops. This includes combining the compounds so the farmer feels like he has more control,” he says.
But these agrochemicals are both highly persistent and highly mobile within the environment. The herbicide atrazine used in Samara Souza’s research remains in water for 100 days before it completely dissolves. Europe banned atrazine 20 years ago, and chlorpyrifos in 2020. Yet Brazil continues to be the main consumer market for these products whose patents aren’t even nationally owned.
In the context of the Amazon, it’s the compounding of climate change impacts with the effects of these agrotoxins that threaten food safety in the region. Here, fish is the main source of protein: some 400 metric tons of tambaqui are consumed in Manaus alone every year. Aside from the health risk, this combination would also mean losses to fisheries and aquaculture productivity in the region.
Yet Brazil has ample alternatives to agrochemicals. Dos Santos cites biological controls for crops: using species that prey on pest insects until their populations have been reduced or eliminated entirely.
“There are other alternatives, including crop rotation and integrated pest management which can even use drones,” dos Santos says. “New generations of family farmers need to have access to the newest science and technology available so they can reduce the use of pesticides and even reduce their costs.”
For instances where water quality has already been compromised, such as downstream of fish farms, INPA is studying what’s known as biofloc technology. This involves the use of microorganisms to improve water quality in farming systems, leading to increased immunity in the animals and, consequently, less need for agrochemicals and other medications.
Citations:
Silva de Souza, S., Rodrigues Bruce, K. H., Custódio da Costa, J., Pereira, D., Sebrenski da Silva, G., & Val, A. L. (2024). Effects of climate change and mixtures of pesticides on the Amazonian fish Colossoma macropomum. Science of The Total Environment, 922, 171379. doi:10.1016/j.scitotenv.2024.171379
Rico, A., de Oliveira, R., Silva de Souza Nunes, G., Rizzi, C., Villa, S., De Caroli Vizioli, B., … Waichman, A. V. (2022). Ecological risk assessment of pesticides in urban streams of the Brazilian Amazon. Chemosphere, 291, 132821. doi:10.1016/j.chemosphere.2021.132821
Schiesari, L., Waichman, A., Brock, T., Adams, C., & Grillitsch, B. (2013). Pesticide use and biodiversity conservation in the Amazonian agricultural frontier. Philosophical Transactions of the Royal Society B: Biological Sciences, 368(1619), 20120378. doi:10.1098/rstb.2012.0378
dos Santos Costa, M., Menezes Da Silva, H. C., Cardoso Soares, S., Favarato, R. M., Feldberg, E., Silva Gomes, A. L., … Matoso, D. A. (2022). A perspective of molecular cytogenomics, toxicology, and epigenetics for the increase of heterochromatic regions and retrotransposable elements in tambaqui (Colossoma macropomum) exposed to the parasiticide trichlorfon. Animals, 12(15), 1945. doi:10.3390/ani12151945
Fernando dos Santos, C., Otesbelgue, A., & Blochtein, B. (2018). The dilemma of agricultural pollination in Brazil: Beekeeping growth and insecticide use. PLOS ONE, 13(7), e0200286. doi:10.1371/journal.pone.0200286
This article by Tiago Da Mota E Silva was first published by Mongabay.com on 17 October 2024. Lead Image: A tambaqui (Colossoma macropomum). Image by Fir0002, GFDL 1.2, via Wikimedia Commons.
What you can do
Help to save wildlife by donating as little as $1 – It only takes a minute.
Leave a Reply