WILLEMSTAD – Curaçao’s less populated western coastline is not necessarily protected from chemical pollution generated elsewhere on the island. New research shows that ocean currents can transport and accumulate human-related contaminants along the western coast, including areas around Westpunt.
The finding challenges the assumption that the highest pollution levels will always be found closest to Willemstad or other densely populated and developed areas.
Researchers examining xenobiotics in Curaçao’s coastal waters found that several chemical compounds repeatedly accumulated along the less populated western coast.
The study points to ocean circulation as an important explanation.
Curaçao is influenced by the northwestward-moving Caribbean Current as well as recurring cyclonic eddies. During the exceptionally wet 2022 research period, persistent eddies reduced the normal flushing of nearshore waters and increased the amount of time substances remained along the coast.
Computer simulations showed that passive substances such as nutrients and pollutants can preferentially accumulate along Curaçao’s western margin because of reduced water renewal combined with continuing inputs from land.
Rainfall was responsible for approximately one-third of the variation in the overall distribution of terrestrial xenobiotics, making it the strongest environmental factor identified by the researchers.
The prevailing type of ocean current was the second strongest factor, accounting for approximately 11 percent. Other factors included water depth, distance from runoff channels, land use, coastal geography, connectivity between coastal zones and population density.
The researchers also found that concentrations could be greater closer to Curaçao’s reefs than at the surface.
Across all sites, xenobiotic abundance approximately half a meter above the reef was on average 1.3 times higher than in surface water. During the 2021 wet season, concentrations near reefs were around 1.5 times higher.
At Westpunt, the difference was even more pronounced in some measurements, with reef-to-surface ratios reaching approximately 1.77 during the 2021 wet season.
Different types of pollutants also followed different geographical patterns.
Plant protection products were detected island-wide, suggesting that currents distribute them far beyond agricultural areas. Human metabolites were prevalent near both Willemstad and Westpunt, while plastic additives, surfactants and other substances associated with domestic use tended to cluster around more urbanized locations.
Pharmaceuticals produced another notable result.
Although these substances are often associated with septic leakage and incomplete wastewater treatment, the study found higher pharmaceutical abundances at some western locations than in central Willemstad.
Researchers believe this could indicate a relatively constant low-level release into the sea, followed by accumulation in areas where coastal water is not flushed away as rapidly. They note that such accumulation can occur even during the dry season and may present ecological and potentially health-related risks depending on the pharmaceutical involved.
The findings mean that controlling pollution only at locations where contaminants enter the sea may not be sufficient.
According to the researchers, exposure around Curaçao is determined by a combination of human activity and the physical movement of seawater. Currents can carry contaminants away from their original sources and concentrate them elsewhere.
This makes pollution generated in one part of Curaçao potentially relevant to coral reefs and coastal ecosystems kilometers away.