Macrophyte Biological Index for Rivers estimation in the waters of Pescara Springs by means of SCUBA dive and orthophotos interpretation

Macrophyte Biological Index for Rivers (IBMR) has been applied to the superficial waters of Pescara Springs (Popoli, Italy) according to Water Framework Directive 2000/60/EC. Two complementary and not mutually exclusive methodologies were performed to evaluate possible differences in taxa identification and cover estimation: boat survey and interpretation of orthophotos and images taken during SCUBA (Self-Contained Underwater Breathing Apparatus) dive. Data from submerged macrophytes were analyzed by means of exploratory multivariate analysis to detect vegetation associations and their correlation with some abiotic factors (water current velocity, substrate granulometry, detritus type, water depth). Six homogeneous tracts were observed according to hydromorphological characters and to vegetation associations; IBMR and Ecological Quality Ratio (IBMR-EQR) were calculated for each of them. On an average basis, IBMR was 7.84 (trophic status: very high) and IBMR-EQR was 0.63 (quality class: scarce). A good concordance was registered by means of Bland–Altman plot between values obtained by the two methods: 0.57 ± 3.07 (mean ± SD) of percent bias. Nevertheless, IBMR failed to correctly describe the trophic status of the surveyed site, possible due to low dissolved oxygen, high pCO2 and HCO3 values.