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Pollutants from fossil fuels are embedded in coral skeletons

A team of researchers from University College London (UCL) has recently made an alarming discovery, finding that pollutants from burning fossil fuels are embedded in coral skeletons. 

This significant finding, published in the Science of the Total Environment journal, highlights corals from Illa Grossa Bay near the Columbretes Islands in the Mediterranean Sea as carriers of carbon particles – specifically, fly-ash or spheroidal carbonaceous particles (SCPs) from fossil fuel combustion. 

Human-induced environmental changes 

Such contamination is a stark indicator of human environmental impact and serves as a historical marker for the onset of the Anthropocene epoch, a period defined by human activities being the dominant influence on climate and the environment.

Corals have long been valued in paleoclimate research for their ability to record environmental data analogous to tree rings, given their slow and regular growth. While traditionally used to study past climatic conditions like water temperature and chemistry, the detection of pollutant particles in corals marks a novel method for examining human-induced environmental changes.

Historic rate of fossil fuel combustion

“The discovery of these pollutants embedded in coral skeletons extend over decades and paint a clear picture of how extensive human influence is on the environment,” said lead author Lucy Roberts, an environmental geochemist at UCL. “It’s the first time we’ve been able to see this kind of contaminant in corals, and its appearance in these deposits parallel the historic rate of fossil fuel combustion in the region.”

Cladocora caespitosa

The study focused on the coral species Cladocora caespitosa, collected from a reef off Castelló, Spain. This coral species is notable for being the only Mediterranean coral capable of forming large reefs, growing at an average rate of about 0.3 centimeters per year. 

The selected site, positioned nearly 60 kilometers from the shore and within a protected marine reserve, minimizes potential local contamination influences.

Corals as natural archives

In the laboratory, the coral samples were dissolved in acid to isolate any pollutant particulates within the skeletons. The researchers utilized microscopes and x-ray analysis to identify and analyze the SCPs, finding a notable increase in contamination between approximately 1969 and 1992, coinciding with rapid industrialization and increased coal consumption in Europe.

This correlation between coral SCP contamination and historical pollution levels supports the concept of using corals as natural archives to monitor pollution trends over time. The study’s findings contribute to the broader scientific endeavor to define the Anthropocene epoch, advocating for the inclusion of SCP presence as a key marker.

Broader implications 

“As it becomes clearer that humans have altered the natural environment to an unprecedented level, these pollutants act as indelible markers, indicating the start of the Anthropocene epoch,” Roberts said. 

“This is valuable to researchers trying to better understand the history of human impact on the natural world and serves as a powerful reminder of how extensive human influence is over the environment,” she concluded. 

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