Newly-funded DFG project is diving deep into the hidden world of subsurface aquifer microbes

Karstified aquifers are a crucial source of drinking water, but excessive agricultural fertilizer use has introduced harmful loads of nitrate. This poses health risks, as the European Union mandates nitrogen levels below 50 mg/L in drinking water. Yet, nitrate levels often surpass this limit in agricultural regions, like Germany's Ammer River catchment, where concentrations have reached 60 mg/L, compared to 1 mg/L downstream.

This gradient of nitrate concentrations along the aquifer hints at intense denitrification. In subsurface, nutrient-poor environments, microorganisms can link nitrate reduction to iron/sulfur oxidation using pyrite in the rock. However, identifying where these microbes thrive remains challenging.

To unravel these mysteries, rock cores were retrieved from the 70-m-deep "Bronnbachquelle" karstic spring catchment, a River Neckar tributary. Additionally, the drilling campaign established a unique, casing-free borehole that will be used as a groundwater well for further studies.

The major goals of this project are to:

1️. Identify denitrifying microorganisms and their capabilities in the carbonate rock from "Bronnbachquelle."

2️. Characterize microbial colonization on synthetic lithic substrates using microcosm experiments.

3️. Assess the impact of borehole drilling on subsurface microbial communities by monitoring water chemistry and microbial community composition.

Diving deeper into these karstified aquifer mysteries promises to unlock valuable insights that will drive forward effective strategies for safeguarding our precious groundwater resources.