{"id":25652,"date":"2026-01-15T18:30:00","date_gmt":"2026-01-15T23:30:00","guid":{"rendered":"https:\/\/www.ecoticias.com\/en\/?p=25652"},"modified":"2026-01-15T06:31:15","modified_gmt":"2026-01-15T11:31:15","slug":"the-mar-menor-hides-an-underground-river-that-no-one-could-see-and-every-year-it-leaves-a-toxic-signature-underwater-where-thousands-of-people-swim","status":"publish","type":"post","link":"https:\/\/www.ecoticias.com\/en\/the-mar-menor-hides-an-underground-river-that-no-one-could-see-and-every-year-it-leaves-a-toxic-signature-underwater-where-thousands-of-people-swim\/25652\/","title":{"rendered":"The Mar Menor hides an underground river that no one could see, and every year it leaves a toxic \u201csignature\u201d underwater where thousands of people swim"},"content":{"rendered":"\n

A hidden underground river carrying mercury has been discovered beneath Mar Menor<\/a>, a well-known coastal lagoon in southeastern Spain. Researchers found that this flow of contaminated groundwater<\/a> quietly delivers about one kilogram of mercury into the lagoon each year. The finding raises new questions about how safe and resilient this tourist hotspot really is.<\/p>\n\n\n\n

The work, led by marine scientist C\u00e9line Lavergne at the Institut de Ci\u00e8ncies del Mar<\/a> in Barcelona, shows that this underground source brings in mercury at levels similar to those from the air and around seventy times more than the Albuj\u00f3n River, the only permanent stream feeding the lagoon. To a large extent, it turns the seafloor into a hidden pipeline for pollution. At the end of the day, that is what makes this discovery so unsettling for people who swim, sail, and fish there.<\/p>\n\n\n\n

What scientists found under Mar Menor<\/h2>\n\n\n\n

Instead of a surface river, the team tracked groundwater<\/a> moving beneath the lagoon floor through what experts call submarine groundwater discharge, which simply means water flowing from coastal aquifers into the sea out of sight. <\/p>\n\n\n\n

By sampling lagoon water, sediments near the beaches, boreholes on land, and the Albuj\u00f3n River, they could map how this invisible flow moves. Their measurements showed that groundwater recirculating through the sediments carries especially high amounts of dissolved mercury.<\/p>\n\n\n\n

\"Satellite
Mar Menor and La Manga, seen from above, where researchers say mercury-tainted groundwater seeps into the lagoon from below each year.<\/figcaption><\/figure>\n\n\n\n

When the researchers added up those measurements, they estimated that this hidden river sends roughly one kilogram of mercury every year into Mar Menor, which is about 2.2 pounds. That load is similar to the mercury that falls directly from the atmosphere and far higher than the amount brought in by the Albuj\u00f3n River. In simple terms, the main drip of mercury now seems to come from below rather than from rain or surface runoff.<\/p>\n\n\n\n

Much of the mercury is what scientists call legacy pollution that was left behind in soils and sediments by decades of mining and farm activity in the region<\/a>. Co-author Andrea G. Bravo notes that \u201ca significant portion of the mercury we measured originates from past activities\u201d and is still moving through the system. For the most part, that means old contamination is being slowly flushed back into the lagoon throughgroundwater<\/a> instead of staying buried.<\/p>\n\n\n\n

From hidden metal to toxic methylmercury<\/h2>\n\n\n\n

Mercury itself is a metal that can harm the brain, kidneys, and nervous system when people are exposed to high levels over time. The most dangerous form in water is methylmercury<\/a>, an organic version that easily builds up in fish and other animals. <\/p>\n\n\n\n

According to the World Health Organization<\/a>, exposure to methylmercury is especially risky for fetuses and young children because their developing nervous systems are more vulnerable.<\/p>\n\n\n\n

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Read More: South Korea has just maintained a stable plasma inferno for six minutes, and scientists say this is a game changer<\/a><\/h3>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\n

In Mar Menor, the study found that places where groundwater meets salty lagoon water near the shore are perfect for turning mercury into methylmercury. These shallow zones tend to be low in oxygen and rich in organic matter, which encourages microbes that carry out this chemical change. <\/p>\n\n\n\n

Researchers reported high methylmercury concentrations in nearshore waters, suggesting that coastal springs and seepage spots can become true hotspots for this toxic form.<\/p>\n\n\n\n

Methylmercury then moves up the food chain so larger predator fish usually carry more of it than the small creatures they eat. For someone ordering grilled fish at a seaside restaurant, that is the link that matters most. <\/p>\n\n\n\n

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