A recirculating flow-through system for toxicity testing with stream-dwelling aquatic benthic invertebrates

The development and use of standardized toxicity test systems and methods a pplicable to stream dwelling benthic invertebrates have not received the sa me attention as test methods developed for still water and sediment associa ted invertebrates. As such, basic toxicological information concerning loti c organisms is generally lacking in comparison with lentic invertebrates. T he requirement of flowing water in test systems with stream invertebrates h as presented technical challenges uncommon to systems using still water or sediment organisms. To alleviate this problem, a new toxicity test system w as developed for stream invertebrates. The new system, referred to as the ' Trent tube', is small in size (17 cm x 30 cm x 9 cm deep), easily construct ed from commonly available materials, relatively inexpensive to build and a daptable to many taxonomic orders of benthic invertebrates. These factors h elp to eliminate some of the technical challenges commonly associated with flowing water test systems and thereby increase the ease of testing and tes t replication. The standard design of the Trent tube is operated as astatic renewal system with a pooled grouping of organisms, but is easily modified for use as a continuous flow-through system that can monitor the responses of individuals. A feature unique to the Trent tube is the ability to monit or multiple responses from individual organisms. When operated as a static renewal system, the Trent tube was successfully used to monitor the respons es of individual Hydropsyche larvae during a 7 week test period. This syste m is easily adaptable to a variety of desired test end points. The basic de sign of the Trent tube system presents a model from which standard toxicity test methods could be developed. (C) 1999 Elsevier Science B.V. All rights reserved.