“…4). (MARGALEF, 1948(MARGALEF, ,1952(MARGALEF, ,1953PRAT et al, 1979PRAT et al, -1986MlLLET & PRAT, 1984;GONZALEZ et al, 1985;GROSSMAN et al, 1985;PALAU & PALOMES, 1986 a,b;RIERADEVALL & PRAT, 1986;PUIG et al, 1987PUIG et al, -1990 ); the high Guadalquivir Basin (DOMEZAIN et al, 1987;ZAMORA-MUÑOZ, 1988;MADRID, 1990 As a group, the studies on fluvial benthos advance two principal themes: community structure (descriptive phase) and indices (biotic indices and water quality). In addition to these two areas of interest appear some studies on community zonation (cases associated with time) and some works presenting wider ecological proposals (MARGALEF, 1947(MARGALEF, , 1960HERRANZ, 1983 PRAT, 1986;PUIG et al, 1987: GARCIA DE JALON et al, 1988FANLO et al, 1989;IMBERT & POZO, 1989;BALTANAS, 1990;PUIG et al, 1991;SOLER, 1991;MALO & PUIG, 1992;; ROLDAN & PUIG, 1992; SOLER & PUIG, 1992).…”