Estudi de la font de Can Verdaguer: origen, evolució de les característiques fisicoquímiques de l’aigua i relació amb els ecosistemes associats

Abstract

The present study takes place in the fountain of “Can Verdaguer” and its associated canal. The area appears inside the municipality of “Sant Gregori”. Geologically, the fountain is located NE of the “Depressió de la Selva”, just on its limit with the “Serralada Transversal”. The main objectives of this project are: 1) to know the geological origin of the water; 2) investigate the evolution of the algae biota along the canal, while the hydrochemical properties of the water change through its path and 3) to study in detail the water chemistry. In order to accomplish these objectives, the following actions have been completed: 1) collect the existent information about the geology of the zone; 2) the development of a geophysical campaign (electrical resistivity tomography); 3) water analysis (pH, dissolved oxigen, water flow, redox potential, temperature, Cl-, Br-, SO42-, F-, Na+, NH4+, K+, Mg2+, Ca2+, NO2-, NO3-, PO43-, total P, total As, total B, total Fe, total Mn, total Rb and total Sr) along 11 sampling points and 4) the study of the algae biota present in the canal sediment by measuring some biological variables (Margalef Index, chlorophyll, biovolume, diatom density per cm2 and weight). Taking into account the previous projects present on the scientific background of this fountain and the ERT profiles, it can be advocated that the deep origin of the water in the “Can Verdaguer” fountain is related to the water infiltration inside the fault of “Llorà” through the “Serralada Transversal”.

According to the hydrochemical point of view, the water of “Can Verdaguer” can be classified as sodium bicarbonate. In addition, it presents a slightly acidic pH, with high concentration of dissolved iron, calcium, sodium and bicarbonates. These chemical parameters are the ones that define, in a more representatively way, the chemical properties of this water system. In relation with the algae biota, it presents in general, a prism morphology with an elliptic base. The main diatom species are: Navicula cincta and Achnanthes minutissima var. Gracillima. About the biological variables measured (Margalef Index, chlorophyll, biovolume, diatom density per cm2 and weight) all of them tend to increase as the distance of the canal increases too. Finally, it has been stated that the algae biota is significantly related with the hydrochemical properties of the water, especially with iron, dissolved oxygen, temperature, calcium and pH