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Into the darkness - a look at underground waterways

Into the darkness - a look at underground waterways

Aquifers and the water table are frequently out of sight and out of mind, but all this changed for Chris Luck when he met François Lefebvre from Vienne Nature…

Delve into the ground beneath our feet and we enter a strange and little known world where creatures have existed for millions of years without ever seeing the light of day. The source of the tap water for most of us in rural France, the world of groundwater and aquifers, is very much alive!

For some, the investigation of this often overlooked ecosystem is the focus of their professional lives. One scientist in particular, independent biology researcher François Lefebvre, has been seeking a very rare and unusual creature that was first discovered in 1955 in an underground river, the Bataillé at Gournay-Loizé in Deux-Sèvres. The creature in question is a minute subterranean isopod crustacean found only in this region and nowhere else in the world - a Gallaselle named Gallasellus heilyi. First found by Gabriel Heily, a Poitevin caver and technician at the CNRS laboratory of Animal Biology at Poitiers University, the creature was described and named in 1956 by Professor Jean-Jacques Legrand.

Since then, ad-hoc sampling by academics and passing cave scientists has found Gallasellus heilyi in the départements of Charente-Maritime and Indre, and a freshwater well at Saint-Denis-d’Oléron. It has a strong genetic connection with a North American species that shows that they were present before the continents separated some 100 million years ago. More recently, in September 2012, two researchers from the University of Lyon in Poitiers for a Séminaire national Gallaselle, identified them in samples from the lavoir (the ancient laundry fed by a spring) at Roches-Prémaries in Vienne.

The state of knowledge on the biodiversity of ground water in this part of France has been very fragmentary and, at most, we have known of the existence of a dozen species (shellfish essentially). It is probable that dozens of species remain to be discovered beneath our feet. Research into the abundance and distribution of the Gallaselle population provides an opportunity to extend our knowledge in many directions, not least into the examination of water quality that is so important for the health of all.


To this end, a study was set up and funded involving no less than twenty different structures and organisations. These include the Universities of Poitiers and Lyon with financing from DREAL and additional support provided by the Fondation LISEA Biodiversité and the Agence de l’Eau Adour-Garonne. Underground cavities such as communal wells, caves and enclosed lavoirs that take in the different underground rivers, streams and aquifers that feed the various watersheds of the region have been selected. From these, François Lefebvre collects samples to analyse (which also includes basic water quality tests). The process of taking samples isn’t really that complicated as I found out when I spent some time with François seeing what is actually involved other than getting frozen stiff in the cold January winds - once is enough!


Having arrived at the chosen well and unloaded everything that would be required including pails, containers and measuring ropes, the cover was removed. François first took measurements to the surface of the water and then to the bottom of the well before collecting various samples of water and taking an accurate temperature reading which, in my ignorance, I thought was surprisingly high but apparently was in the normal range at 11°C. Basic tests for levels of nitrates, oxygen, and various minerals were taken and found to be in the ‘acceptable’ range although the nitrate level was pushing the limit. Of course, this is not the interesting part which takes place later back at the laboratory. Here the sample can be put under the microscope to view the stygofauna (any fauna that live in groundwater systems or aquifers) which are invisible to the naked eye.

Alongside recording the species present, there is another aspect to these surveys. The very presence of these organisms gives us an indication of the water quality - especially important considering the volumes of pesticides used over the last 70 years.

As the sampling and analysis continues, the presence and variety of stygofauna is expected to teach us much about the quality and evolution of our local water sources. And, as the management of our environment above ground alters, the impact below ground is one we should all be watching carefully.

Aquifer Organisms

BythinelleBythinelle: Bythinella are a genus of very small freshwater snails or aquatic gastropod molluscs in the family Amnicolidae. 2-4 mm in size, the different species are often to be found in springs although in this case they inhabit groundwater and caves. In France a particularly high diversity of these snails are to be found. But, due to their limited range and their special and easily destroyed habitat, they are at risk of becoming endangered species.


Caecosphaeroma burgundum is an isopod that inhabits ground water. Isopods are an order (group) of crustaceans that includes woodlice, sea slaters and their relatives. According to Armand Viré, generally considered the French founder of ‘biospéologie’, the freshwater underground species come from marine ancestors. They ascended the rivers and entered the groundwater where the stability of the environment (temperature, hardness, etc.) would have favoured their survival when the climate changed. We now only have fossil records of their marine ancestors.

NiphargusNiphargus ladmiraulti is one of over 300 described species and subspecies of the genus Niphargus, the largest genus of freshwater amphipods. Most of the species inhabit subterranean waters and constitute a substantial part of Europe’s groundwater biodiversity. Different species inhabit virtually all types of subterranean waters such as cave waters, subterranean flows and lakes, fissure systems, wells and springs, as well as brackish, mineral and thermal waters. In addition, about a dozen species live in surface waters such as forest ditches, sphagnum moss or small streams. These are large enough to see and you are quite likely to have them in water you scoop from the bottom of a well here.

Hydracarien: Hydrachnidiae, also known as ‘water mites’, are a group covering more than 40 families and 5,000 species found in freshwater and marine habitats. The Hydracarina are properly subaquatic and can be found in surface water but there are some that live deep in the dark. They are all thought to have evolved from land dwelling species that adapted to an aquatic environment.

 © Living Magazine. Originally published in June 2015