A recent study conducted at Tel Aviv University (TAU) and the Steinhardt Museum of Natural History showed that antibiotics and laxatives were found to pollute corals at 40 meters in the Gulf of Eilat.
The study was led by Prof. Noa Shenkar of TAU’s School of Zoology and her doctoral student, Gal Navon, in collaboration with the hydrochemistry laboratory led by Prof. Dror Avisar at TAU’s Porter School of Environment and Earth Sciences.
Corals are invertebrate animals that eat plankton and belong to a large group of animals called Cnidaria (“stinging needles”). Living together as coral reefs, they protect coastlines from storms and erosion, provide jobs for local communities, are a source of food via fisheries and new medicines, attract tourists, and offer recreation opportunities.
More than ten kinds of antibiotics and laxatives consumed by patients have been found in samples collected in Gulf of Eilat corals – not only in shallow waters at depths of five to 12 meters but also in deep waters at 30 to 40 meters down.
Sulfamethoxazole, an antibiotic used for respiratory and urinary tract infections, was found in as many as 93% of the corals they tested.
Although pharmaceutically active compounds (PhACs) are increasingly found in marine environments, their presence in coral reefs, already under threat from various stressors, has remained unexplored. The marine environment, mainly tropical coral reefs, constitutes a cornerstone of global biodiversity, supporting countless species and providing vital ecosystem services.
However, despite their ecological and socio-economic importance, coral reefs face mounting threats from human activities, including overfishing, the introduction of invasive species, and habitat pollution and destruction.
The results, published in the journal Environmental Pollution, are titled “Detection of 10 commonly used pharmaceuticals in reef-building stony corals from shallow and deep sites in the Red Sea.”
Drug testing of the corals
The research team took samples from 96 reef-building stony corals, some of which lay more than 30 meters below the ocean surface. The results showed that regardless of the depth, none of the coral samples were free of drug residues.
“In this first-of-its-kind study, we conducted a large-scale investigation to detect pharmaceuticals in corals,” said Shenkar. “We sampled reef-building stony corals representing two types, Acropora sp. and Favites sp. We were surprised to find an extensive presence of medications even in the deep-water corals that usually escape contaminations affecting corals in shallower areas.”
The researchers obtained a list of Israel's most commonly used pharmaceuticals from the largest public health fund, Clalit Healthcare Services. Testing for 18 of these compounds, they detected 10 in the coral samples. None of these samples, retrieved from either shallow or deep water, was found to be drug-free.
The ten pharmaceuticals found in the corals belonged to different categories –, laxatives, proton pump inhibitors, statins, antidepressants, antibiotics, blood-pressure medications, antiplatelet agents, and calcium channel blockers.
Effects on marine organisms
Upon entering a marine environment, PhACs can persist, bioaccumulate, and exert various adverse effects on marine organisms, including altered physiological processes, impaired reproductive success, and increased susceptibility to disease.
“These medications are taken by humans to affect a certain receptor or biological pathway, and they can also impact other organisms. Previous studies 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.
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.” Shenkar said.
“These medications save lives, and we have no intention of requesting people to reduce their use,” Shenkar declared. “But we must develop new sewage-treatment methods that can effectively handle pharmaceutical compounds. Also, we must dispose of old medications in ways that do not harm the environment".
“Stony corals build coral reefs, and the types we studied are very common in the Gulf of Eilat,” added Navon. “Coral reefs are a cornerstone of marine biodiversity. They provide food, shelter, and spawning sites to numerous species and support the human fishing and tourism industries.
This ecosystem is under pressure today due to climate change, pollution, and overfishing. Pharmaceuticals in coral tissues add another layer of concern, indicating that human activities contaminate faraway marine environments.
The detection of 10 different PhACs in coral tissues underscores the need for conservation efforts to mitigate human contamination in coral reef ecosystems.
These findings highlight coral reefs' vulnerability to pharmaceutical pollution.