The potential importance for spring conservation of residual habitats after flow capturing: A case study

Springs are characterised by seasonal fluctuations of the main environmental parameters (e.g., temperature and alkalinity), which are dampened if compared to those of other freshwater habitats, and they integrate direct and indirect impacts oil the drainage basin in space and time (CANTONATI et al. 2006). This peculiar environmental stability is often reflected by the occurrence in these habitats of taxa relevant for aquatic biodiversity conservation. Springs are endangered habitats. Anthropogenic disturbances like water abstractions or land use practices in the catchment area are causing a marked decrease of the total number of natural springs. The main threat to springs is the continuous water abstractions for a variety of purposes (e.g., drinking water, irrigation, and hydropower stations). Springs with the highest discharge are already being used, even within protected areas, where strict regulations should limit their use. In 1998 at the end of a comprehensive study on 30 natural springs within the Adamello-Brenta Natural Park (PNAB, Italian Alps: CANTONATI 1998a), 5 of these springs were chosen for a long-term ecological research programme. In the frame of this research (CANTONATI et al. 2005), in 2004 the spring of Ponte delle Cambiali, one of the few valley-bottom, large, and only partially altered flowing-spring habitats on 9, siliceous substratum remaining in the area, was added to the sampling sites considered for long-term ecological research. Rather suddenly, the local municipality decided to use this spring as a source of drinking water for the whole Genova valley (mainly sparse cottages and cattle barns used only in summer), and in June 2005 the construction works for water abstraction started. The relatively high discharge assured the persistence of the water flow in an area only slightly down-stream of the former natural spring mouth (through pipes releasing the excess water from the concrete capturing structure). Even though the capturing event had been announced only late, and Our sampling design could not be modified to follow it in every detail, we decided to use the data we collected before and after capturing to try to provide the first elements oil the potential value of residual habitats for spring biodiversity conservation. We focussed mainly on diatoms, which are usually present in springs with a high number of taxa, several of which are sensitive indicators of mineral content, alkalinity, nitrate, and other factors (CANTONATI & ORTLER 1998), and on zoobenthos orders that could reflect water flow and benthic substratum characteristics (ILMONEN & PAASIVIRTA 2005). Data oil ecomorphology and macroscopic phytobenthos were collected as well, although not presented in detail in this paper.