An in situ system for exposing aquatic invertebrates to contaminated sediments

An in situ system was developed for exposing benthic invertebrates directly to contaminated sediments without exposure to natural overlying waters. Th is system was used to expose fourth instar Chironomus riparius Meigen larva e for 48 h at 13 uncontaminated river sites across southeast England and at sites along the contaminated River Aire in Yorkshire. Recovery of survivin g C. riparius from uncontaminated sites was good (>65%) except when indigen ous predatory insect larvae were trapped within test systems. Recovery of s urvivors from the uncontaminated upstream site in the River Aire was also g ood (mean survival at Gargrave = 70%), but survival at the two contaminated downstream sites was significantly lower (mean survival of 17.5% at Esholt and 10% at Calverley Bridge). This study has shown that sediments can be i solated from overlying water and effectively bioassayed in situ.