Relationships between metals and hyporheic invertebrate community structure in a river recovering from metals contamination

Biota and chemistry from hyporheic samplers were used to describe environmental changes, after treatment of mine drainage, in the shallow hyporheic zone in the upper Arkansas River, Colorado, U.S.A. Samples were collected (1992-1997) from above and below the mine drainage source, and further downstream where a historically cleaner tributary enters the system. Hyporheic metal concentrations were high during spring runoff at the impacted site even after initiation of treatment, but declined after several years. Correspondence analysis and increased invertebrate taxa richness suggested that hyporheic macroinvertebrates were recovering at the previously impacted site. Differences in substrate between sites and high water flows in 1995 also appeared to affect hyporheic communities. High taxa richness and abundance, taxa unique from those found at the surface, and high concentrations of metals found in the shallow hyporheic zone suggests that sampling this zone is important for monitoring recovery of polluted streams.