A first approach to a faunistic crenon typology based on functional feeding groups

Springs are ecomorphologically and faunistically diverse freshwater ecosystems. Their limnological classification has been afocus of interest since crenic research began. Despite many attempts to include the crenic fauna in the classification of springs, thereis no faunistic crenon typology. Over a three-year period we investigated the macroinvertebrate assemblages and the physical,chemical and ecomorphological conditions of 82 springs in the Swiss Jura Mountains, north-western Switzerland. Based on thesedata we selected the 25 least-disturbed springs to develop a faunistic crenon classification. Based on functional feeding groups wedifferentiated three crenon groups. An analysis of similarities and nonmetric multidimensional scaling for the substratum typessupported the crenon groupings. In general we can distinguish between springs that are dominated by scrapers and characterized bya lotic environment, and those that are mostly inhabited by filtering collectors, associated with a lentic environment. Those twocrenon types are the extremes of a continuum. Particular crenon forms, such as those with extensive carbonate deposits, lie betweenthese extremes. This third group is characterized by gathering collectors and shredders. Using this approach we can distinguishfaunistic crenon types, based on functional feeding groups, which reflect the abiotic conditions within the springs. We provide afoundation for a faunistic crenon typology which now can be tested in other landscapes and will then be applicable to other lowmountain ranges in Europe.