Earthworms as Test Organisms in Ecotoxicological Assessment of Toxicant Impacts on Ecosystems - Earthworm Ecology - page 284

16

Earthworms as Test Organisms
in Ecotoxicological
Assessment of Toxicant
Impacts on Ecosystems

Adriaan J. Reinecke and Sophié A. Reinecke

Department of Zoology, University of Stellenbosch, Stellenbosch, South Africa

CONTENTS

Introduction....................................................................................................................................299
The Test Organisms.......................................................................................................................300
Acute Toxicity Testing with Earthworms......................................................................................301
Chronic Toxicity Tests and Sublethal Effects...............................................................................303
Earthworm Toxicity Testing for Regulatory Purposes..................................................................304
The Use of Earthworm Biomarkers and Understanding Bioavailability......................................305
Estimating Environmental Exposure of Earthworms to Toxicants...............................................308
Earthworms in Bioassays, Microcosms, and Model Ecosystems.................................................308
Field Toxicity Tests Using Earthworms........................................................................................309
Residues in Earthworms and their Role as Biomonitors and Bioindicators................................310
Risk Assessment Using Earthworms.............................................................................................311
Decisions on Managing Estimated Risk of Chemicals to Earthworms........................................314
Conclusions....................................................................................................................................315
References......................................................................................................................................316

INTRODUCTION

Concerns about sustaining soil fertility in agricultural land, in which a variety of toxicants are used
for crop protection; risks of chemicals leaching into drinking water; contamination of soil; and
detrimental effects of contaminants on the nontarget living environment have grown. This is also
evidenced by the realization that endocrine-disrupting effects of some toxicants can have severe
implications for ecosystems as well as human health. This has also resulted in a strong and growing
awareness of the importance of soil biodiversity and its role in providing ecosystem services
(Bengtsson 1997; Daily 1997). Environmental scientists and legislators are today more aware of
the need to protect the structure and functioning of soil ecosystems in which the decomposer
community performs especially vital functions. Many toxic materials accumulate through food
webs, and the detritivore-decomposer levels are often the first to be affected. Organic matter, which
serves as a valuable resource for the soil biota, and the soil itself are the ultimate sinks for most
contaminants. Legislation in many countries has focused the attention of scientists on the need for
sensitive organisms from the soil environment for use in research, in environmental monitoring, as

299