New Baltic bacteria linked to ocean warming | Science| In-depth reporting on science and technology | DW | 25.07.2012
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Science

New Baltic bacteria linked to ocean warming

Vibrio bacteria are usually found in warm waters, but new research has found them in the cold Baltic Sea as a result of rising temperatures. Controlling the spread will be hard.

A team of scientists from Britain, Finland, Spain and the United States says it has the first hard evidence to link rising ocean temperatures in Northern Europe with the emergence of various strains of Vibrio bacteria.

Vibrio bacteria are normally found in warm, tropical marine environments but have now been detected in the usually cold Baltic Sea.

They belong to a group of bacteria which - depending on the strain - can cause gastroenteritis or cholera in humans if raw or undercooked shellfish are consumed, or through exposure to contaminated seawater.

Published in the journal Nature Climate Change, the findings also suggest the warming patterns in the Baltic Sea are manmade.

Rising temperatures

The research focuses on sea surface temperature records and statistics of Vibrio cases. It shows the Baltic Sea warmed at a rate of 0.063 to 0.078 degrees Celsius from 1982 to 2010.

Baltic Sea shoreline

The Baltic Sea is becoming a Vibrio breeding ground

And for each year the ocean temperature rose by one degree, the number of Vibrio cases increased by 200 percent.

Vibrio bacteria have emerged previously in other cold regions such as Chile, Peru and the US Pacific northwest.

But these outbreaks were attributed to sporadic events rather than responses to long-term climate change.

"This is the first study to show a direct correlation between global climate change and the emergence of Vibrio diseases," says Professor Stefan Schild from the Institute for Molecular and Biosciences at Graz University in Austria. "It is very novel."

Current science suggests that climate change is not only warming oceans but also causing more rain. The higher rain levels reduce salt content in estuaries and costal wetlands - and many types of marine bacteria thrive in warm sea water that has low salt levels.

"Vibrio likes more salt than what is contained in normal fresh water ponds but not as salty as real marine water," says Schild.

Vibrio infections

One of the authors of the report, Craig Baker-Austin of the UK-based Centre for Environment, Fisheries and Aquaculture Science says most Vibrio infections are preventable.

"A simple measure would be to recommend that people with underling risk conditions and especially those with obvious wounds, which are a major route to infection, do not enter the sea during 'at risk' periods," Baker-Austin said in an email to DW.

Researcher at Robert Koch-Institut Berlin handles petri dish

Researchers want a dedicated body to collect data on Vibrio bacteria

But Baker-Austin says there is no simple strategy for controlling the spread of Vibrio bacteria. He says different types of bacteria will emerge as oceans warm and coastal areas become less saline.

Need for more data

The various forms of Vibrio "are naturally occurring bacteria" that thrive in warm and tropical marine environments.

But more research is needed to understand the link between climate change and the emergence of some infectious diseases.

"Often, very important epidemiological information such as the timing, location, type of bacterium, and the age and sex of patient, is not gathered, making it very difficult to assess risk properly," says Baker-Austin.

Other scientists like Professor Stefan Schild at the University of Graz say Europe needs a dedicated body to collect data on Vibrio bacteria and other organisms.

"We need some form of surveillance - which we currently don't have," says Schild.

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