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Bacteria Thrive as Ocean Warms

Bacteria Thrive as Ocean Warms

Scientists have been working to identify the ways in which our warming seas are affecting other Earth systems, including life in the ocean. One research team recently showed that warmer ocean temperatures could make you sick through the rise of marine bacteria called Vibrio.

Species of Vibrio bacteria are ubiquitous throughout the oceans. They thrive everywhere from surface waters to the deep sea, and from the coast to the open ocean. You may have heard about the bacteria from cases where it has sickened people with vibrosis, the effects of which can range from cramps and nausea to death in the most severe cases. According to the Centers for Disease Control and Prevention, most of the 80,000 Americans who contract the illness each year fall ill after eating contaminated seafood, particularly raw oysters. It’s also possible to contract the illness through exposure of an open wound to seawater.

Although Vibrio are widespread, found mainly in association with marine plankton organisms, they tend to flourish in higher concentrations when water is warm. That’s why most infections occur between May and October. And on the longer term, research led by Luigi Vezzulli of the University of Genoa in Italy, shows that warming sea surface temperatures are also playing a role in the spread of this bacteria and their associated diseases.

The map above, based on data from the UK Met Office Hadley Center, shows how surface temperatures in the North Atlantic Ocean changed between the period from 1890–1958 and the period from 2000–2011. Dark orange and red areas saw the most warming. The warming water coincides a rising abundance of Vibrio, changes in climate, and an increase in the reported cases of vibriosis, which the scientists say indicates a direct correlation.

To confirm the correlation, the scientists investigated bacterial DNA from archived formalin-preserved plankton samples collected by the Continuous Plankton Recorder Survey over the past half-century (1958–2011). In areas of warming, data from historic plankton sampling sites (marked on the map with boxes) showed increases in Vibrio bacteria abundance.

Next, they showed that increases in Vibrio abundance were related to changes in climate patterns depicted by NASA’s Northern Hemisphere Temperature (NHT) index—a measure of atmospheric and ocean temperatures over the northern half of the planet—and the Atlantic Multidecadal Oscillation (AMO). Finally, all of these changes parallel the rise in Vibrio-related illnesses documented along the U.S. Atlantic Coast and in Northern Europe shown in the graphs above.

“According to our study, the observed increase in the number of Vibrio infections in the human population in recent years—including infections from so called ‘flesh eating bacteria’ such as Vibrio vulnificus—could be a direct consequence of dramatic ocean warming over the last few decades,” Vezzulli said.

NASA Earth Observatory images by Joshua Stevens, using data from Vezzulli, Luigi, et al. (2016). Story by Kathryn Hansen.

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