The Tribune

By EARYEL BOWLEG

Tribune Staff Reporter

ebowleg@tribunemedia.net

SHARKS off Eleuthera have been found with cocaine, caffeine and common painkillers in their blood, according to a new study that highlights the growing reach of human pollution in Bahamian waters.

The peer-reviewed research, published in Environmental Pollution, found contaminants of emerging concern in multiple shark species sampled from nearshore waters around the island. The study marks the first reported detection of caffeine and acetaminophen in sharks anywhere in the world, and the first report of diclofenac and cocaine in sharks from The Bahamas.

Researchers analysed blood samples from 85 sharks, including tiger sharks, blacktip sharks, Caribbean reef sharks, Atlantic nurse sharks and lemon sharks. The samples were screened for a range of substances, including pharmaceuticals, stimulants and illicit drugs.

Four contaminants were detected: caffeine, cocaine, acetaminophen and diclofenac. They were found in 28 sharks across three species: Caribbean reef sharks, Atlantic nurse sharks and lemon sharks.

Caffeine was the most commonly detected compound. It was present in 12 Caribbean reef sharks, all five contaminated Atlantic nurse sharks and ten lemon sharks. Cocaine was detected in one Caribbean reef shark and one lemon shark. Acetaminophen appeared in three sharks, while diclofenac was detected across all three affected species.

The findings are significant because sharks are apex or near-apex predators and play a critical role in maintaining marine ecosystems. In The Bahamas, they also underpin a major tourism industry built around shark diving and marine conservation.

The study focused on south and central Eleuthera, where sharks were sampled from several coastal sites. Contaminants were detected at Aquaculture Cage, Boathouse Cut, Kemps Creek, Hallig Beach and Page Creek. No contaminants were detected in sharks sampled at Schooners, Schooners Deep, Broad Creek or Savannah Sound.

The Aquaculture Cage site recorded the highest number of detections and the highest concentrations of several compounds in Caribbean reef sharks. Researchers said this pattern likely reflects local human activity rather than species-specific differences.

They noted that the site is frequently visited by liveaboard vessels and tour operators for shark-diving excursions, suggesting that vessel traffic and associated wastewater may be contributing to contamination even in offshore environments.

While the study does not conclude that the detected substances are directly harming sharks, it found differences in some biological markers between contaminated and uncontaminated animals.

In Caribbean reef sharks, those with detectable contaminants had lower urea levels and higher lactate levels. In Atlantic nurse sharks, contaminated individuals had lower triglyceride levels. Lemon sharks with detectable contaminants showed lower triglyceride and lactate levels.

Researchers said these changes could indicate shifts in metabolism or stress responses, but they cautioned that the findings do not establish a direct cause-and-effect relationship.

The study also noted that contaminants were detected only in a subset of animals and that blood samples primarily reflect recent exposure rather than long-term accumulation. It added that comparisons across species and locations were limited by the overlap in sampling locations for certain species.

Still, the presence of these substances in sharks highlights the growing reach of human-derived pollution in Bahamian waters.

The researchers pointed to tourism-related development, vacation homes and increasing wastewater discharge as likely contributors to the introduction of pharmaceuticals and other contaminants into coastal ecosystems.

They also highlighted caffeine as a key indicator of human activity, noting that it was the most frequently detected compound and is commonly used as a marker of wastewater contamination.

The study was conducted by researchers affiliated with the Cape Eleuthera Institute and international institutions, with approval from the Department of Environmental Planning and Protection. It used non-lethal sampling methods to collect blood from the sharks before releasing them.