14 years ago, the government of Mazatlán and federal authorities announced the rescue of the local estuarine system that contemplated the Estero de Urías, a place that houses a biological wealth of more than 73 species of waterfowl. However, the project was not implemented and today this body of water is one of the most contaminated by microplastics in the world.
The project was presented by the National Water Commission (Conagua) in 2011, during the Mazatlán National Clean Beaches Meeting, and was entitled “Sanitation of the Urías Estuarine System”. The plan promised to be developed by the local government and the Ministry of Environment and Natural Resources (Semarnat). Even bootable worktables were integrated, but none of that prospered.
“The alteration of water quality has generated a downward trend in the capture of marine species that thrive there. The limitation also extends to recreational use, caused by mistrust between the native population and the source of infection that the problem generates.” This is how the project considered the situation of the Mazatlán estuarine system.
Currently, Estero de Urías receives sewage from the city and tons of garbage that carry streams, canals and tributaries that cross the urban area of the most important tourist destination in Sinaloa, known as “The Pearl of the Pacific”.
Tires, bags, armchairs, wheelbarrows, face masks, Christmas spheres, refrigerators and containers have invaded the bowels of the 873 hectares of red, black and white mangroves that extend around this coastal lagoon of approximately 12.5 kilometers of surface.
Garbage accumulates in layers inside the mangroves of the Urías estuary. Photo: Raquel Zapien.
All possible forms of pollution weigh on this estuarine system, which is visited annually by about 20,000 waterbirds of 73 different species, according to counts carried out by Juanita Fonseca, a specialist in shorebirds and collaborator of the Hemispheric Network of Reserves for Shorebirds. The biological wealth of the place includes fish, mollusks, crocodiles, turtles, iguanas, frogs and various species of snakes.
“Many people from Mazatlán don't know it [the Urías estuary], they see it as a dirty place, like a wastewater place,” laments Alexis Guadalupe Romero Osuna, a professor at the Center for Technological Studies of the Sea 08 (CETMAR).
Together with his students, he has examined the stomachs of fish and mollusks purchased at nearby piers to verify the presence of microplastics in these organisms.
These small particles, the result of the degradation of larger plastics, are also present in the sediments of Estero de Urías. This is indicated by a study carried out at the Institute of Marine Sciences and Limnology (ICMyL) of the Autonomous University of Mexico (UNAM), which chronologically details how these polymers have accumulated in the bed over the past 100 years, with PET (polyethylene terephthalate) being the most abundant so far.
The research reveals that the levels of microplastics in this coastal wetland are among the highest in the world, together with bodies of water in the United States, China, Saudi Arabia, South Korea, Spain, Turkey, Brazil and Uruguay, where similar study methodologies were applied to estimate the age of its sediments.
Where do microplastics go?
In water, plastics find different destinations after being fractured by up to one thousandth of a millimeter. These microplastics have been found in fish from Estero de Urías that are usually caught by coastal fishermen for human consumption. In 2021, for example, the presence of plastic particles was reported in the digestive tracts of 552 specimens of 13 different species.
Most plastic waste consisted of threads measuring less than one millimeter, followed by fragments between two and four millimeters and a few pieces of plastic several centimeters long.
The finding was obtained from a study carried out by researchers from the Faculty of Marine Sciences of the Autonomous University of Sinaloa, Faculty of Chemical Sciences and Engineering of the Autonomous University of Baja California and the UNAM.
In total, 1,384 plastic waste particles were recovered from the fish. Half of the remains (51.2%) are nylon fibers, a synthetic compound used in the manufacture of textiles and industrial parts. These fibers commonly come from washing clothes.
About a third (36.6%) of the microplastics detected in the mouth, stomach and intestine of finfish are made of polyethylene, which is used in the manufacture of bags and containers. Another portion corresponds to polypropylene (7.3%) and polyacrylic (4.9%); the former is used in the manufacture of household goods and the second in the construction industry.
In wetland fauna, its accumulation can block digestive systems and reduce reproductive capacity; it is also likely that contaminants are transferred to humans through consumption with consequences that are still uncertain and are being investigated.
The rescue simulation
The possibility that the estuary would finally be serviced emerged in August 2011 with the announcement of the “Sanitation of the Urías estuarine system, in Mazatlán, Sinaloa”. As the name suggests, the promise was not only to decontaminate the Urías estuary, but the entire lagoon complex, including the La Sirena and Infiernillo estuaries, then comprised of 18 square kilometers that communicate with the Pacific Ocean.
In the foreground, you can see the Infiernillo estuary, which connects at the end with that of Urías. Photo: Marlenne Manzano Sarabia.
The emblematic project comprised 110 actions divided into five challenges: strengthening environmental culture based on responsible practices; freeing the estuarine system from solid waste; reducing the accumulation of waste and hazardous substances; discharging treated wastewater in compliance with the standard and recovering the surface of the estuarine system. The investment was estimated at 300 million pesos, about 16 million dollars today, with gradual actions to 2030.
However, the rescue project was never carried out.
This journalistic team sent 12 requests for information to the authorities involved at the three levels of Government, to access details of the monitoring plan, results, minutes and photographic evidence of work sessions following its announcement. The answers were coincidental: there is no such information.
Mongabay Latam and Causa Natura sent questions to Conagua and the Government of Mazatlán to find out why the program was not implemented and why no steps have been taken to clean up the Estero de Urías. Until the publication of this report, only the municipality of Mazatlán responded that “Conagua is the one who directed the project and is responsible for operating it.” As a local government, they assured that they only participated in the planning process, specifically in the diagnosis.
Waste water receiver
This ecosystem has historically been used as a receiver for drains that overflow from sewers and broken pipes in various parts of the city. In addition, an uncalculated number of homes in the tourist resort of Isla de la Piedra discharge their wastewater into mangroves because they have never had drainage and sewerage services.
“Everything has always been dumped into the estuary or the beach,” admits Silvia Lizárraga Fuentes, resident and president of the civil association Colonias de la Isla en Acción.
The estuary adjoins the industrial and naval area of the port of Mazatlán. Photo: Raquel Zapien.
Four of the five wastewater treatment plants that serve the city are discharged into the same estuary: Santa Fe, El Castillo, Urías I and Urías II. The latter was built to replace the El Crestón plant, which operated on the waterfront, and which was dismantled starting in 2021 because it looked bad to the thousands of visitors who transit the area and where a new cruise terminal is planned to be built.
Treatment plants fail to completely eliminate all contaminants from wastewater, says Ana Carolina Ruiz Fernández, a researcher at the Institute of Marine Sciences and Limnology of the National Autonomous University of Mexico (UNAM), Mazatlán Unit. For this reason, treated water discharges also increase the concentration of organic matter in the coastal lagoon, which, unlike the sea, has less water exchange and purification capacity, says the expert in geochemistry and geochronology.
The synthetic fibers detected by the UNAM in sediments and fish also arrive this way.
“It has been found that treatment plants bring a lot of microplastic as waste from washing machines. All this domestic water reaches the treatment plants, they concentrate it and they are discharging it into the estuary”, confirms the researcher.
That would explain why about two-thirds of the microplastics found in sediment analysis are synthetic clothing fibers.
As if that weren't enough, the lagoon water has also been documented to contain hydrocarbons and mercury, one of the most dangerous heavy metals to human health, which can be ingested through the consumption of contaminated fish and seafood.
Those who suffer from this pollution are the most vulnerable. According to the National Population Council (CONAPO), of the 35 colonies near the estuary, where around 50,000 Mazatlcos live, 37.5% are highly marginalized. In these areas, 31 percent of the population lives in overcrowding, 34 percent of people over 15 have no basic education and 22 percent lack access to health services.
Alexis Guadalupe Romero Osuna, a biochemical engineer, an expert in Aquatic Resources, recognizes that drainage and waste collection are the public services that fail the most in the area. This lack, he argues, causes people to dump gray water into the estuary and throw garbage in it.
In addition to pollution, this ends up affecting the residents' sense of belonging, because in the absence of municipal attention, they themselves see the ecosystem as “a place that serves to dispose of what no longer serves them”.
In its report “Impacts of marine litter on environmental justice and plastic pollution”, the United Nations Environment Program (UNEP) points out that plastic pollution mostly affects marginalized communities and communities that live very close to plastic production and waste sites, with health risks associated with the consumption of seafood infested with toxic micro and nanoplastics.
The Circle of Neglect
After the cleanings, the garbage comes back. Photo: Raquel Zapien.
Leticia Alvarado Fuentes, director of the Municipal Planning Institute (IMPLAN) of Mazatlán, acknowledged that the estuary area has suffered structural abandonment due to a lack of coordination between federal and municipal authorities.
“There are any number of omissions because it is not clear what are the powers of the agencies, particularly the municipal ones, to care for and protect that area that is frankly at imminent risk of ceasing to be a natural space and becoming a highly contaminated area,” he said.
For Professor Romero Osuna, the lack of government attention also generates the idea that this natural space, refuge and feeding area for countless living beings, is not important.
“If people see that the authorities don't give it the importance it deserves, maybe they'll apply the 'why am I going to take care of him if others don't? '” , refers.
Ignorance is another factor that favors lack of attention, Romero points out. “A lot of people in Mazatlán don't know it and see it as a dirty place, but when they visit it they realize that it's beautiful.”
That's why guided tours are organized for elementary school students and local universities to the nursery where CETMAR students grow mangrove seedlings, a species protected by Mexican environmental legislation. With these plants, they reforest the shore of the estuary that adjoins their school yard to restore the landscape and transform the consciousness of those who participate.
The first opportunity for community conservation could come if researcher Juanita Fonseca succeeds in nominating Estero de Urías as a site of the Hemispheric Network of Reserves for Shorebirds, a designation that seeks to protect these species and their habitats on the American continent. To achieve this, the specialist has been monitoring the shorebirds that use this space in recent years, but she needs partners to update the information and meet the naming criteria, she says.
Recovery is still possible
Until now, the “rescue” of Estero de Urías lies in the cleaning actions carried out by citizen organizations with the support of educational institutions and that seem to have no end: just as tons of plastics are extracted, so they arrive again.
There is so much waste stuck in the estuary that an islet with mangroves is already known as the “Garbage Island”. There, the Viva la Ola organization has carried out mass cleaning that includes all kinds of incentives: from contests to safaris with the assistance of expert guides, breakfasts and 2x1 passes to recreational spaces.
Added to this effort are the cleaning and the floating barrier installed by the organization Maz ConCiencia between the Infiernillo and Urías wetlands to prevent garbage from reaching bodies of water.
Companies and government agencies have also organized to remove garbage in the city's wetlands, as part of the National Environmental Restoration Program (PNRA) 2025-2030, but since there is no institutional program for local management of urban solid waste, waste continues to reach those places.
Currently, the only way to confine the almost 700 tons of garbage generated per day in the city is to deposit it in an open-air landfill, near the estuary. From there, the polluting liquids filter out with rain, end up in aquifers, or drain into the wetland. This has been the case for more than 35 years.
Tons of garbage have been removed from the estuary by citizen groups. Photo: Raquel Zapien.
Dr. Ana Carolina Ruiz Fernández believes that despite high levels of contamination of organic matter, plastics and toxic substances, the system still performs ecological functions, although it needs rehabilitation.
“We have to close these sources of pollution and let nature itself do its work, I think it is recoverable,” he says.
Stopping polluting discharges and better managing urban solid waste, with efficient collection, transport, treatment and final disposal, would help improve their environmental conditions, says the UNAM researcher.
“If we continue on this path, we are going to end up killing it irrecoverably, but it is possible to make this place a much better place if we stop affecting it with what we already know we don't have to do,” he warns.
The academic community, fishermen and organizations are already present, now there is a need for rescue from government authorities.
The estuary is waiting.
* This text is part of a journalistic alliance between Mongabay Latam and Causa Natura.
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