Evaluation of Caging Designs and a Fingernail Clam for Use in an In Situ Bioassay

摘要: Two cage designs and fingernail clams(Sphaerium fabale) were evaluated for theirsuitability use in situ bioassays toassess the ecological condition of a stream andpredict recovery potential. One design(referred to as tray design) was modified plastictray about one-fourth full small gravels andcovered with 1 mm fiberglass mesh. The second tube-plates) consisted shortplexiglass tubes one-third gravelsand attached horizontally plexiglass plate. Oneend each tube faced into current; both endswere covered Cages containing clams weredeployed at reference impacted (test) sites forperiods 70 135 d. Growth survival theprimary endpoints evaluated, but tube-platesallowed isolation individual so that natalityalso could be an endpoint. Results ofbenthic macroinvertebrate surveys, performed foranother study, included help validate bioassayresults. Both yielded good quantitative,site-specific results clam growth;results natality, though, less conclusive. Clam growth generalagreement benthicmacroinvertebrate community surveys. At site wherethe mostdepauperate, mortality always rapid. asite where macroinvertebratecommunity only slightly than themost site, almost alwayssignificantly lower sites. Survivalof significantly reduced <25 d thissite some trials, other trials there waslittle mortality. minimally clamsurvival similar found sites,and differences not detectableuntil after 40 50 exposure. tube-platedesign easier use, allowed more flexibility inselection response parameters, required lesshandling time test animals, thus, this thepreferred design. Our demonstrated thateither bioassay design can used toaugment monitoring assessment programs. Their useas predictor recovery, however,requires further evaluation.