Global warming = more Vibrios in the North Sea?

It is known that global warming causes an increase of the sea surface temperature (SST) and that this has a negative long-time impact on eukaryotes. There are only a few investigations on the effects on prokaryotes because they are considered to be less sensitive to climate changes. This study by Vezzulli et al. (2012) focuses on the long-time effects of increasing SST on the prokaryotes of Vibrio spp. and is one of their first investigations on the correlation of Vibrio abundance and increasing SST.

Vibrios are gram-negative bacteria and belong to the Gammaproteobacteria. They are found on many abiotic and biotic substrates such as chinitous plankton which can be used as nutrient reservoir. Vibrios are pathogenic towards humans and animals and are linked to the increasing mortality of marine animals and human infections. The most popular Vibrio species is Vibrio cholera, the pathogen that causes Cholera. 

In their study Vezzulli et al. examine their hypotheses that, firstly, there is a positive long-time correlation between the increase in SST and the abundance of Vibrio spp. Secondly, they tested whether there is an increase in the dominance of Vibrio in plankton-associated communities which is linked to the increasing SST. 

To investigate these hypotheses the researchers used 55 CPR (Continuous Plankton Recorder) samples from estuaries off the Rhine and the Humber (southern and northern North Sea) from 1961 - 2005. All the samples were taken in August of each year. The SST data were taken from the HadSST data set. They found that the Vibrio abundance increased off the Rhine and is positively correlated to the increasing SST. The estuary off the Humber did not show the same result. No significant correlation between the Vibrio abundance and the increasing SST was detected there. This can be explained by the temperature conditions in which Vibrios thrive best (16 – 18 °C), which were reached and also exceeded off the Rhine but not off the Humber. The SST explained 45 % of the variance in the Vibrio data in the southern North Sea. SST together with the total number of copepods (from WinCPR database) explained even 50 % of the Vibrio variance. This is the first time that it is shown that a long-time increase of SST has an increasing effect on the abundance of warm-water Vibrios associated with plankton. Furthermore pyrosequencing showed that Vibrios became dominant within the plankton-associated community. 

Vezzulli et al. conclude that there is a change in plankton-associated bacterial communities due to increasing SST in the southern North Sea and that the dominance of Vibrio is increasing (including human pathogenic species like Vibrio cholerae). They suggest further research on how increasing SST influences the structure of bacterial communities in other global regions and research on the effects on ecosystems, animal and human health. 

This paper is a good base to understand the problematic spread of pathogenic bacteria due to global warming. Vezzulli et al. investigated the linkage between Vibrio spread and increasing human diseases in their recent paper (2016).

Reviewed paper:

Vezzulli, L., Brettar, I., Pezzati, E., Reid, P. C., Colwell, R. R., Höfle, M. G., & Pruzzo, C. (2012). Long-term effects of ocean warming on the prokaryotic community: evidence from the vibrios. The ISME journal, 6(1), 21-30.

Further reading:

Vezzulli, L., Grande, C., Reid, P. C., Hélaouët, P., Edwards, M., Höfle, M. G., ... & Pruzzo, C. (2016). Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic. Proceedings of the National Academy of Sciences, 201609157.