FACTORS INVOLVED IN THE BIOGEOGRAPHIC DISTRIBUTION OF MICROBIAL DIVERSITY IN SUBSURFACE WATER OF THE LAURENTIDES REGION, QUEBEC

The factors involved in the biogeographic distribution of microorganisms at a regional scale, are multiple and still misunderstood, especially in groundwater. Recent studies suggest that groundwater composition, which is strongly linked to the geology of the aquifer, explains most of the prokaryote diversity living in the water. To test this hypothesis, we sampled 62 wells and measured 48 biochemical parameters of the water (iron, nitrate, pH, etc.) in the Laurentide region, Quebec, within an area of 20 000 km2. The microbial community composition has been analyzed using high-throughput-sequencing of archaeal and bacterial 16S RNA genes then gathered as operational taxonomic unit (OTU). The scale of this sampling allows us to compare local and regional diversity. Moreover, the large quantity of biogeochemical parameters and their significant variability across wells gives us valuable information on which element has the most influence on the diversity. The results show that the bacterial and archaeal diversity are very different across the wells. These differences seem to be mainly explained by differences in the groundwater biogeochemical parameters. Wells with a high concentration in inorganic carbon have a large number of autotrophic bacteria such as Omnitrophica or Sulfuricurvum. These observations can also be observed with high iron concentration where we find a higher relative amount of iron reducing bacteria. Understanding the process shaping the microbial distribution in groundwater ecosystem is crucial to maintain the balance of biogeochemical cycles of water while being aware of the impact of a water composition change on the microorganisms.