Temporal and spatial patterns of coarse particulate organic matter and macroinvertebrate distribution in a low-order apennine stream

We described the microdistribution of benthic macroinvertebrates in a 50 m riffle segment of the Rio del Giovo (Sassello, NW Italy) during a period of rapid loss of leaf mass, from March to May 2003. We analyzed the relationship between the taxonomic composition and functional organization of benthic communities and the availability of coarse particulate organic matter (CPOM), as well as the influence of micro-environmental characteristics (water velocity, depth, and substratum). Patches without CPOM hosted specialized communities. The temporal variation of CPOM influenced the distribution of functional feeding groups in the riverbed. In particular, shredder assemblages were widespread in the riverbed when CPOM was abundant, but when this resource became scarce and localized, their density was related to the availability of allochthonous organic detritus.