Antibiotic Contamination In Oceans Threatens Us And Environment
October 16, 2012

Oceanic Antibiotic Contamination Threatens Both Us And Environment

April Flowers for - Your Universe Online

Antibiotics play a critical role in modern medicine. We take them to fight diseases, we give them to our pets, our food animals, even our plants. But what happens to those antibiotics after they pass through our systems? How do they affect the rest of the world?

That is the question researchers from the University of Gothenburg have been asking, specifically how do these antibiotics affect the bacteria in the ocean. The research team spent August in Sisimiut on the western coast of Greenland, studying antibiotic resistance and the effects of antibiotic emissions on bacteria communities in marine sediments. The bacterial flora they studied live in layers of sediment and clay on the seabed.

"We know very little about what happens to antibiotics that end up in the ocean, but several substances can accumulate in sediments where biodegradation occurs extremely slowly," says researcher Maria Granberg.

In Europe alone, more than 100,000 tons of antibiotics are used every year. Some 30 to 60 percent of these pass through humans and animals without being changed at all. And through hospitals, municipal sewage, fish farms and run-off from agriculture and landfills, these substances make their way into the ocean.

The team from Gothenburg focused their study on the potential effects of accumulating antibiotics in the seabed.

"Our aim is to document the sea's natural microbial structure and function as well as resistance patterns, so that we can determine if and in what way things change as a result of human activity," says Maria Granberg.

Greenland was an easy choice for the team because it has areas where the water is essentially untouched by civilization, the likes of which do not exist around Sweden. However, Greenland also has areas with highly polluted waters. This duality makes it the perfect location for studying the environmental impact of antibiotics.

"Greenland has no sewage treatment whatsoever, which means that waste water from inhabited areas is discharged straight into the sea," says Maria Granberg. "So Greenland is home to both very clean and very polluted waters, which is great for comparing environmentally pristine areas with polluted ones."

Substances that are not easily biodegraded are often stored in the soft sediments on the seabed which act as a kind of reservoir. Even substances that aren't released directly into the sea like Greenland´s sewage eventually make their way into this sediment via rainwater. This means that antibiotics can affect marine sediment ecosystems over a long period. Among other things, the team´s results indicated that this has detrimental effects on natural marine communities of bacteria.

"The presence of antibiotics in the marine environment is worrying as it can result in widespread resistance to antibiotics in marine bacteria with unknown consequences for the spread of resistance genes to bacteria that can reach humans through the consumption of seafood and fish."

The bacteria that the team is studying are important on a global scale as they metabolize both nitrogen and carbon. Molecules rich in nitrogen and carbon are linked to phenomenon known as hypertrophication, the over-enrichment of water that can lead to the over-stimulation of phytoplankton reproduction. These “blooms” of phytoplankton can result in hypoxia, or oxygen depletion in the water, and even large-scale climate change.

Critical to the researchers´ concerns is the fact that resistance genes can also be transferred between different bacteria communities.

"We know very little about how antibiotics affect natural systems and how antibiotic resistance develops and spreads in these systems," says Maria Granberg.

"This knowledge is, however, vital if we are to identify the sources of, and understand, the mechanisms behind the development of antibiotic resistance, which constitutes a threat to both the functioning of ecosystems and human health."