Detection of trace elements in freshwater macrobenthic invertebrates of different functional feeding guilds: A case study in Northeast Italy

Trace elements are common contaminants in aquatic ecosystems; their detection in biota yields information on their availability in the environment and provides an indirect indication of freshwater ecological status. We analyzed samples of freshwater macrobenthic invertebrates from six watercourses in Friuli Venezia-Giulia (Northeast Italy) to verify whether trace elements accumulation is related to their ecological status sensu Water Framework Directive (WFD), and to determine tropic level influences on the accumulation of 18 trace elements in macrobenthic communities. Observed concentrations could be in line with results of ecological status assessment defined by the WFD, in fact two sites classified as “Moderate” had the highest trace elements content. The genus Calopteryx (Odonata, predator) was positively correlated with Be, Cr, Fe, Mn, Mo, Ni, Sn, and V (ρS range 0.777–0.844). Positive correlations were also determined for the genus Rhyacophila (Trichoptera, predator) with Cu (ρS = 0.757), suggesting bioaccumulation in macroinvertebrate tissue. Ephemeroptera of the genus Caenis (collector-gatherers) were positively correlated with Be, Fe, Mn, Pb, Sb, and V (ρS range 0.757–0.802), indicating that ingestion of sediment is the most effective uptake of these metals. Results of this study, albeit preliminary, showed that trace elements detection in aquatic macrobenthic invertebrates is a useful analysis for obtaining information about the status of freshwater course. Our study provides evidence for a greater accumulation of trace elements in predators and collector-gatherers, suggesting that the tropic level of macrobenthic communities influence the accumulation of trace elements.