Shallow water hydrothermal vents

Hydrothermal vents have been discovered across the globe’s oceans in areas of ocean ranging from abyssal to intertidal. Though there have been many studies conducted upon deep-sea hydrothermal vents there has been comparatively little done upon shallow water hydrothermal vents; that is vents that exist at a depth of 200m or less. The author has outlined the possibility that both phototrophy and chemotrophy work in tandem  in the shallow water vent ecosystem as the vent is closer to the surface of the water and therefore has access to sunlight. Another key difference between these vents and their deep-sea counterparts is that the plumes of volcanic water that erupt from the shallow water vents reach the surface, which can have quite a profound impact on the ecosystems around it. Whereas the plumes of deep-sea hydrothermal vents are restricted to quite a narrow zone.

This study analysed the bacterial communities of two different vents over eight samples, four from a white vent and four from a yellow vent. The authors used pyrosequencing to produce 32 bacterial and archaeal DNA and RNA based tag libraries. They also attempted to address the biogeochemical that are mediated by the microbial community.

The results of statistical testing revealed that the pyrosequencing produced estimates of richness that were higher than the analyses of clone libraries, the data for this was not shown within the paper which would have otherwise helped to reinforce that point by providing evidence which can be seen by the reader. However, it must also be noted that the inclusion of such data may have served only to confuse or swamp the reader with a number of different figures.  There was also evidence to suggest that there is a high dominance of abundant taxa and generally low richness of communities. Further analysis showed that there is quite a high degree of diversity within the dominant taxa which can perhaps suggest that many species are responsible for the high diversity of the bacterial and archaeal libraries. It was also found that the libraries separated into distinct clusters that correspond to the two vents.

As was predicted by the authors Cyanobacteria were very prevalent within the samples taken and made up a large proportion of the RNA pool, this provides further evidence for the idea that photosynthesis takes place in tandem with chemolithotrophy. It has also been noted that this is unique to shallow water vents for reasons given above. The significance of this is yet to be discussed and has not been covered within this paper. It could be speculated that the presence of Cyanobacteria co-occurring with chemolithotrophic bacteria could be due only to the fact that sunlight can reach the shallow water vents. Another possibility is that the Cyanobacteria form a symbiotic relationship with other bacteria such as members of the genus Thiomicrospira as these bacteria have the capacity to obtain Carbon from CO₂, though what the Cyanobacteria would gain from the relationship is not apparent. 

ZhangY., Zhao Z., Chen CA., Tang K., Su J., Jiao N.,  2012, Sulfur Metabolizing Microbes Dominate Microbial Communities in Andesite-Hosted Shallow-Sea Hydrothermal Systems, PLOS one, 7 (9), e44593