Corals are absorbing human drugs, and not just in shallow water

When we think of medications, we mainly envision relief from ailments or protection against diseases. However, a recent study has revealed an unforeseen impact of these beneficial drugs – they’re winding up in our coral reefs.

A team of researchers from Tel Aviv University and the Steinhardt Museum of Natural History have discovered traces of 10 prevalent pharmaceuticals in coral samples.

These samples were not just from some random shallow locales, but from both shallow and deep sites in the Gulf of Eilat. Even Sulfamethoxazole, an antibiotic we humans use for respiratory and urinary tract infections, marked its presence in a staggering 93% of the tested corals.

Human drugs in coral reefs

The study was led by Professor Noa Shenkar from TAU‘s School of Zoology and PhD student Gal Navon.

The researchers collaborated with the Hydrochemistry laboratory, which is led by Professor Dror Avisar at TAU’s Porter School of Environment and Earth Sciences.

“In this first-of-its-kind study, we conducted a large-scale investigation for detection of pharmaceuticals in corals,” said Professor Shenkar.

The team sampled 96 reef-building stony corals of the Acropora sp. and Favites sp. varieties. They were picked from shallow sites (5–12 meters) and deeper sites beyond the reach of casual divers (30–40 meters).

Medications in deep-water corals

The alarming presence of medications was found even in the deep-water corals, which are generally spared from the contaminants that affect their shallow-dwelling counterparts.

So, how did these medications end up in the corals? The researchers focused on the most commonly used pharmaceuticals in Israel, courtesy of Clalit Health Services.

Out of 18 common medications, the team detected traces of 10 different drugs in the coral samples. Not one sample, from either shallow or deep water, was found to be drug-free.

“What does the presence of pharmaceuticals in corals actually mean? Clearly, the corals did not receive a prescription for antibiotics from their doctor,” said Professor Shenkar.

“These medications are taken by humans to affect a certain receptor or biological pathway, and they can also impact other organisms.”

Impacts of drugs in corals

If you thought the problem ends with antibiotics, brace yourselves. The 10 medications detected spanned diverse categories, from blood pressure and antiplatelet agents to antidepressants and laxatives.

So, what do these pharmaceuticals do to the corals? Well, the reality is as shocking as it is peculiar.

“Previous studies, conducted by both our lab and others, have revealed many examples of this negative impact: estrogen from birth control contraceptive pills induces female features in male fish, impairing reproduction in certain species; Prozac makes some crabs aggressive and reckless; and antidepressants damage the memory and learning abilities of squids,” said Professor Shenkar.

“There is no reason to believe that corals should be immune to such effects. For instance, if our pharmaceuticals should disrupt the spawning synchrony of coral populations, it would take us a long time to notice the problem, and when we do, it might be too late.”

Reverberations in the ecosystem

“Coral reefs are a cornerstone of marine biodiversity,” noted Gal Navon, drawing attention to the importance of these underwater structures.

“They provide food, shelter, and spawning sites to numerous species, and support the human fishing and tourism industries. The presence of pharmaceuticals in coral tissues adds another layer of concern, indicating that human activities even contaminate faraway marine environments.”

What is the solution? Professor Shenkar said that new sewage treatment methods must be developed that can effectively handle pharmaceutical compounds.

“Also, each of us must dispose of old medications in ways that do not harm the environment.”

Cycle of contamination

In a chilling revelation, Professor Shenkar warns about how these medications in coral reefs might find their way back to us.

“Ultimately, these drugs come back to us. I know people who avoid medications, but when they eat a fish, they might unknowingly consume a ‘cocktail’ of drug residues absorbed by the fish from the marine environment.”

In essence, what we put into the environment has a way of coming back to haunt us – a grim reminder to strive for a more sustainable and responsible future.

The study is published in the journal Environmental Pollution.

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