Figure 4. Growth and reproductive response, and bioaccumulation of zinc and mercury in adult E. fetida worms cultivated on test dredged material and control soil in 1-kg cylinders

ERDC TN-DOER-C22

September 2001

Figure 4. Growth and reproductive response, and bioaccumulation of zinc and mercury in adult E. fetida

worms cultivated on test dredged material and control soil in 1-kg cylinders

matter contents. However, at this time use of the enchytraeid worm, E. crypticus, for dredged

material toxicity screening needs additional development and testing.

SUMMARY: Three CDFs in the Great Lakes area with known predredging contaminant types and

levels were initially selected for verification of dredged material chemical composition, evaluation

of nutrient levels, and preliminary survey of landscape and biota: Monroe, MI, Manitowoc, WI,

and Bayport, WI. Typical characteristics of the dredged materials that set them apart from most

soils are the low organic matter content (compared to soils), low bulk density, relatively high

plant-available phosphorus, and low nitrate-nitrogen concentrations. All sites are characterized by

the presence of a ponded area, an intermediate area occupied by herbaceous vegetation typical for

highly disturbed systems, and a forested upland area. Invertebrate diversity and abundance varied

per site, both being highest at sites where the dredged material had become consolidated, the water

table had decreased, and vegetation had been established. Springtails and earthworms were fairly

common, and are considered as suitable test organisms for these dredged materials. Dredged

material of the Monroe site was selected for further bioassay testing of inorganic contaminants.

Suitable plant species for testing were found to be Cyperus esculentus, yellow nutsedge, and

Cynodon dactylon, common bermudagrass. Eisenia fetida, an earthworm, was identified as a