The influence of land use on freshwater macroinvertebrates in a regulated and temporary Mediterranean river network

Abstract

Freshwater macroinvertebrates face numerous stressors at different spatial scales, challenging river managers to identify the most appropriate, to initiate a successful river restoration. To address this, 45 samples from 13 sites located in a regulated and temporary Mediterranean river network were analyzed. Sites were separated according to hydrology and classified into four zones based on land use. Chemical analysis was undertaken prior to macroinvertebrate sampling, and a chemo-biological classification was performed. Canonical correspondence analysis (CCA) and analysis of similarities were used to identify statistical differences between the various groups. Unacceptable quality according to the Water Framework Directive 2000/60/EC was revealed for 60% of samples. Significant correlations were detected between land use and biological indices. Agriculture was the major factor influencing macroinvertebrate distribution, and significant taxonomic differences were identified between natural and agriculturally impacted sites. Flow regime alterations from water regulation and desiccation resulted in significant reduction in macroinvertebrate density. The small difference between explained/unexplained variance (45%/55%, CCA) suggests that land use and local in-stream factors together influence macroinvertebrate assemblages. We conclude that in regulated/temporary rivers, land use and flow-related pressures exert strong influence on freshwater invertebrates and should be given equal importance as local in-stream factors, for sustainable river restoration.