Seasonal and interannual variability of macroinvertebrate reference communities and its influence on bioassessment in different Mediterranean stream types
Sánchez-Montoya, M.M. Suárez
published: May 1, 2009
ArtNo. ESP141017404008, Price: 29.00 €
We investigated the seasonal changes in macroinvertebrate reference communities in four Mediterranean stream types (temporary, evaporite calcareous at medium altitude, siliceous headwaters at high altitude, and calcareous headwaters at medium and high altitudes) and the interannual changes in the two headwaters stream types in Spain. Eighty-eight seasonal reference sites distributed into 23 basins were sampled on three occasions (spring, summer and autumn of 2003), and 18 interannual reference sites distributed in 6 basins were sampled in the autumn of 2003, 2004 and 2005 to examine this temporal variability. Interannual reference sites were a subset of seasonal reference sites. The analysis of similarity (ANOSIM) performed on Bray-Curtis similarity distances, using presence-absence data, showed no seasonal or interannual changes in the macroinvertebrate communities. The influence of seasonal and interannual variability was also tested in all the stream types using 18 macroinvertebrate metrics classified as richness, index, multimetric index, tolerance/intolerance and diversity. ANOVAs showed no seasonal differences in any of the studied metrics for temporary and evaporite calcareous at medium altitude and most of the metrics in the two headwaters stream types. This suggests the suitability of using a single season approach for the biomonitoring purposes of these metrics. Conversely, the seasonal differences detected in the metrics related with EPT (Ephemeroptera, Plecoptera and Trichoptera) and OCH (Odonata, Coleoptera and Heteroptera) taxa in calcareous headwaters indicate possible differences in the relative presence of macrohabitats (riffles and pools) as a result of flow variation. No interannual changes were detected in any of the metrics except EPT/OCH in siliceous headwaters. However, the large variability in the annual rainfall in this study area suggests that this three-year study period may be too short to assess the effect of climatic variations on the ecological status assessment. In general, the lower temporal variability (measured as seasonal and interannual coefficients of variation) of the taxon richness metric (S) and the two studied indices (IBMWP and IASPT), compared with the other metrics, make them a priori robust indicators to assess ecological status in Mediterranean streams.