Juliette Rosebery, Francisca C. Aguiar, Sónia R. Q. Serra, Simone Ciadamidaro, Maria Teresa Ferreira, Gerald Dörflinger, N. Flor, C. Chauvin, Gorazd Urbanič, Camilla Puccinelli, J. Ferreira, Sergi Sabater, Andrea Buffagni, Eva Papastergiadou, Cristiana Vieira, Maria Rita Minciardi, Jaume Cambra, Laura Mancini, Stefania Erba, M. Ferréol, Iakovos Tziortzis, Stefania Marcheggiani, Elisabet Tornés, Maria João Feio, Antoni Munné, François Delmas, Narcís Prat, Mateja Germ, P. Manolaki, Carmen L. Elias, Salomé F.P. Almeida, UNIVERSITY OF COIMBRA INSTITUTE OF MARINE RESEARCH COIMBRA PRT, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), UNIVERSIDADE TECNICA DE LISBOA INSTITUTO SUPERIOR DE AGRONOMIA LISBOA PRT, UNIVERSITY OF AVEIRO DEPARTMENT OF BIOLOGY AND GEOBIOTEC AVEIRO PRT, PORTEGUESE ENVIRONMENTAL AGENCY PRT, WATER RESEARCH INSTITUTE CNR IRSA BRUGHERIO ITA, UNIVERSITY OF BARCELONA DEPARTMENT OF PLANT BIOLOGY ESP, Ecosystèmes aquatiques et changements globaux (UR EABX), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), MINISTRY OF AGRICULTURE WATER DEVELOPMENT DEPARTMENT CYPRUS CYP, Milieux aquatiques, écologie et pollutions (UR MALY), UNIVERSITY OF LJUBLJANA DEPARTMENT OF BIOLOGY LJUBLJANA SVN, NATIONAL HEALTH INSTITUTE ROME ITA, UNIVERSITY OF PATRAS DEPARTMENT OF BIOLOGY PATRAS GRC, SALUGGIA RESEARCH CENTER ENEA SALUGGIA ITA, CATALAN WATER AGENCY ESP, UNIVERSITY OF BARCELONA DEPARTMENT OF ECOLOGY BARCELONA ESP, UNIVESITY OF GIRONA INSTITUTE OF AQUATIC ECOLOGY GIRONA ESP, Instituto Catalán de Investigación del Agua - ICRA (SPAIN) (ICRA), INSTITUTE FOR WATER OF THE REPUBLIC OF SLOVENIA SVN, and UNIVERSITY OF PORTO DEPARMENT OF BIOLOGY PORTO PRT
The present report describes a three-step approach that was used to characterize and define thresholds for the Least Disturbed Condition in Mediterranean streams of four different types, regarding organic pollution and nutrients, hydrological and morphological alterations, and land use. For this purpose, a common database composed of national reference sites (929 records) from seven countries, sampled for invertebrates, diatoms and macrophytes was used. The analyses of reference sites showed that small (catchment100 km(2)) siliceous and non-siliceous streams were mainly affected by channelization, bank alteration and hydropeaking. Medium-sized siliceous rivers were the most affected by stressors: 25-43% of the samples showed at least slight alterations regarding channelization, connectivity, upstream dam influence, hydropeaking and degradation of riparian vegetation. Temporary streams were the least affected by hydromorphological changes, but they were nevertheless affected by alterations in riparian vegetation. There were no major differences between all permanent stream types regarding water quality, but temporary streams showed lower values for oxygenation (DO) and wider ranges for other variables, such as nitrates. A lower threshold value for DO (60%) was determined for this stream type and can be attributed to the streams' natural characteristics. For all other river types, common limits were found for the remaining variables (ammonium, nitrate, phosphate, total P, % of artificial areas, % of intensive and extensive agriculture, % of semi-natural areas in the catchment). These values were then used to select the list of reference sites. The biological communities were characterized, revealing the existence of nine groups of Mediterranean invertebrate communities, six for diatoms and five for macrophytes: each group was characterized by specific indicator taxa that highlighted the differences between groups.