Deep-sea corals contaminated with human drugs, researchers warn
Israeli scientists on Monday revealed the presence of pharmaceutical compounds, including antibiotics and laxatives, in corals collected from the Gulf of Eilat. The findings challenge assumptions that deeper marine environments are insulated from human pollution.
Coral reefs in the Gulf of Eilat. Photo by École Polytechnique Fédérale de Lausanne/TPS-IL
Coral reefs — often referred to as the “rainforests of the sea” — are vital to marine biodiversity and built primarily by colonies of small marine animals called coral polyps. These tiny creatures secrete calcium carbonate, which forms the hard, rock-like structures associated with reefs. Over time, these structures grow and create vast, complex habitats that provide food, shelter, and breeding grounds for countless marine species.
In a first-of-its-kind research, scientists from Tel Aviv University led by Prof. Noa Shenkar studied two coral species Acropora sp. and Favites sp., which are essential components of the reef ecosystem. Their study, published in the peer-reviewed Environmental Pollution journal, raised serious concerns about the environmental impact of human pharmaceuticals on marine ecosystems.
The research team sampled 96 reef-building corals from shallow sites (5-12 meters) and deeper locations (30-40 meters) in the Gulf of Eilat. Every coral sample contained traces of pharmaceuticals.
Among the 10 detected compounds were sulfamethoxazole, a commonly used antibiotic, found in 93% of the samples, along with other medications such as blood pressure drugs, antidepressants, and statins. The team tested for 18 pharmaceuticals, drawing from a list of commonly prescribed medications in Israel obtained from Clalit Health Services.
“We were surprised to find such extensive contamination even in deep-water corals, which are generally thought to be less affected by pollutants compared to shallow-water species,” said Shenkar.
Pharmaceuticals enter the marine environment primarily through sewage systems that fail to filter out these compounds effectively. Once in the water, these medications can affect marine life in unpredictable ways. She pointed out that drugs designed to target human biological systems can have far-reaching consequences on other species.
“What does the presence of pharmaceuticals in corals actually mean?” Shenkar asked. “Clearly, the corals did not receive a prescription for antibiotics from their doctor.”
Previous studies have shown that pharmaceuticals can have disturbing effects on various marine organisms. For example, estrogen from contraceptive pills has been found to induce female characteristics in male fish, impairing their reproductive abilities, while antidepressants have made certain marine animals, like crabs, more aggressive and less cautious.
Corals are unlikely to be immune to these effects. If medications interfere with the reproductive cycles of corals, such as their spawning synchrony, it may take years to notice the full extent of the damage, the researchers stressed.
“The contamination of coral tissues with pharmaceuticals underscores how human activities are affecting even remote marine environments,” said Gal Navon, co-author of the study. “These drugs are saving lives, but their unintended environmental impacts must be addressed.”
While the medications found in the corals are essential for human health, Shenkar stressed the importance of improving waste treatment methods to prevent further contamination. Current sewage treatment systems are inadequate at filtering out pharmaceutical compounds before releasing treated water back into the environment.
“Each of us has a role to play in protecting the environment,” said Shenkar. “We need better sewage treatment technologies that can handle pharmaceutical waste. Additionally, people should dispose of old medications properly to prevent them from entering water systems.”
She added, “Ultimately, these drugs come back to us. Even people who avoid medications might unknowingly consume drug residues through contaminated seafood.”
