Warming Atlantic Ocean leads to rise in marine bacteria

Rising sea surface temperatures in the North Atlantic are likely to be behind a recent surge in cases of diarrhoeal diseases from marine bacteria in northern Europe and the US east coast, a new study says.

In their analysis that goes back to 1958, the researchers show that levels ofVibriobacteria – which can cause illness in humans and even death – have been increasing as sea surface temperatures rise.

Further ocean warming as a result of climate change could exacerbate this spread of marine bacteria, the researchers say, potentially bringing more human infections in future.

Marine bacteria

There are around 110 different types ofVibriobacteriafloating around in our oceans. They aretypically foundin warm, slightly salty coastal waters and river estuaries.

Some of these bacteriacause sicknessin people and animals. Humans pick them up by consuming water or seafood that carries the bacteria, or through cuts in the skin when swimming.

The most well-knownVibrioischolera腹泻病,会导致股票ere dehydration and death if not treated.

This study considers other strains ofVibriobacteria, such asVibrio vulnificusandVibrio parahaemolyticus, which cause similar, though usually less severe, symptoms. These types of illness are known collectively as “vibrosis”, which can lead to complications, such as blood poisoning.

Previous researchhas linked outbreaks ofVibrioinfections around the world to warm sea surface temperatures. Warmer conditions mean alonger summer windowforVibriobacteria to grow and a greater chance of their survival. This conclusion has been reached in studies ofChile,Peru,Israeland theBaltic states.

The new study, just published inProceedings of the National Academy of Sciences, says that a warming Atlantic Ocean is the main reason for an “unprecedented” number ofVibriocases in North Atlantic countries in recent years. This includes a spate of casescontracted by swimmersduring the European summer heatwave in 2006.

Plankton sampling

One of the main limitations for scientists trying to work out how ocean warming is affectingVibriobacteria is the availability of data.

Bacteria are typically measured by microbiologists by collecting and analysing water samples, says lead authorDr Luigi Vezzulli, anassociate professor in microbiology at theUniversity of Genoa.However, as he explains to Carbon Brief, this isn’t without difficulty:

Vezzulli and his colleagues found a way round this problem by instead analysing samples of tiny marine creatures calledzooplankton, on whichVibriobacteria tend to hitch a ride.

Scientists have been collecting samples of plankton in the North Atlantic since 1958 via the Continuous Plankton Recorder (CPR)survey. The CPR actually gets its name from theinstrumentthat, when towed behind ships, collects plankton over huge areas of ocean.

Using the samples from nine locations – shown in the map below – the researchers analysed the DNA of the preserved plankton to create a record of howVibriobacteria numbers have changed over the past six decades.

The findings show that concentrations of the differentVibriobacteria have increased in line with rising sea surface temperatures (SSTs) for eight of the nine North Atlantic locations.

The only exception was at Newfoundland. This is likely because, despite a warming ocean, SSTs in this region still average around 7C, the paper says, which is a bit cold for mostVibriobacteria.

You can see how sea surface temperatures in the North Atlantic have changed over the 21st century in the map below. Coastal regions of western Europe and Canada have warmed the most – by as much as 1.5C in some places, as shown by the red shading. Vezzulli says it’s clear that SSTs andVibriobacteria are linked:

Marine bacteria in a time of climate change

随着北大西洋的温暖和浓度s ofVibriobacteria have increased, the number ofVibrioinfection cases in northern Europe and the US Atlantic coast have also risen, the paper says.

There could be several reasons for this, the researchers note, such as people being more likely to go out swimming in warm conditions. But the data suggest that the number and spread ofVibriobacteria in the water is a strong factor.

This means the rising SSTs could be leading to moreVibrioinfections in humans, the paper says:

Therefore, the continued rise in global SSTs in future years may exacerbate the growth and spread ofVibriobacteria, the researchers conclude.

The study is a “stunning collaboration that integrates major disciplines, including climate, oceanography, microbiology and public health,” saysProf Drew Harvell教授the department of ecology and evolutionary biology atCornell University, who wasn’t involved in the study. She tells Carbon Brief:

Another conclusion from the study is that better monitoring forVibrioinfections may be necessary, Vezzulli says:

This means that doctors and hospitals in European countries are not currently required to inform their government when they treat someone with aVibrioinfection. More comprehensive data collection onVibriocases would help scientists keep tabs on how these diseases are being affected by climate change, Vezzulli concludes.

Update: This article was updated on 08/08/16 to remove references to cholera as the study refers only to non-cholera Vibrio infections.

Main image: Triathlon training – athlete swimming. Credit: microgen/E+/Getty Images.