Land use influences organisms living underground

by Ori Schipper, Swiss Federal Institute of Aquatic Science and Technology
October 22, 2024

Four fifths of Switzerland’s drinking water comes from hidden underground aquifers. Numerous groundwater extraction sites tap into these reserves. Drinking water supplies are under increasing pressure. “In order to fulfil the quality criteria, some extraction sites have to be taken off the grid or water from impacted sites has to be mixed with less impaired water,” says aquatic ecologist Mara Knüsel, who is currently completing her doctorate in Professor Florian Altermatt’s research group at the aquatic research institute Eawag and the University of Zurich.

In recent years, Knüsel and her colleagues have been working intensively on researching small creatures that are at home in dark and cold water: groundwater amphipods. They resemble tiny shrimps, but unlike the differently pigmented freshwater amphipods on the surface, they are white and blind. They play an important role in the function of groundwater ecosystems.

In their latest article, which has just been published in the journal Ecological Applications, the researchers link the occurrence of amphipods to the type of land use on the Swiss Central Plateau. The researchers often found amphipods at groundwater extraction sites in the middle of a forest, whereas they encountered amphipods much less frequently at groundwater extraction sites near farmland. The groundwater at the extraction sites close to crops also tended to be more contaminated with nitrate than at the sites surrounded by forest, which indicates poorer drinking water quality.

However, Knüsel’s colleague Roman Alther points out that it would be premature to conclude that the water quality is poor because amphipods are absent. “Hydrogeology also plays a role,” he explains. “Factors such as the structure of the local groundwater aquifer, including pore size and water chemistry, can also influence whether or not amphipods are present.” The researchers therefore regard the presence or absence of the small organisms more as a supplementary indicator. “As an indication that the biology at a particular location may be impaired,” says Alther.

Keep reading: https://www.eawag.ch/en/info/portal/news/news-detail/land-use-influences-organisms-living-underground/

Read the Ecological Applications paper: https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/eap.3040