Mutation Research 489 (2001) 97–122 Effects of contaminants on genetic patterns in aquatic organisms: a review Natalia M. Belfiore a,∗ , Susan L. Anderson b a Department of Animal Science, University of California, Davis, CA 95616, USA b Bodega Marine Laboratory, University of California, Davis, Bodega Bay, CA 94923, USA Received 2 April 2001; received in revised form 9 July 2001; accepted 19 July 2001 Abstract There is increasing awareness of the need to evaluate the effects of contaminants at the population level. Genetic techniques offer a powerful approach to assess contaminant-induced changes in populations. Yet studies to date are relatively few and not always carefully designed to maximize the utility inherent in this approach. We present a summary of contemporary genetic assessment methods and a review of published studies of genetic effects in field-exposed aquatic organisms. We discuss evaluations of genetic patterns that use genetic adaptation, allozyme variation, and molecular genetic (DNA) variation. Direct tests of genetic adaptation are very effective in establishing a concrete, and potentially deleterious population-level effect of contaminant exposure, but they are difficult to accomplish with most field-exposed organisms. Allozyme surveys are relatively simple and common, and may provide data that are suggestive of contaminant effects. However, these are rarely conclusive, primarily because few allozyme loci are variable and these few loci represent extremely small portions of the genome. Molecular genetic techniques have the potential to be very effective. But, there is a tendency to emphasize the power of the techniques, rather than the underlying causes of the molecular genetic patterns observed. The strength of the conclusions of each study varies widely, partially derived from variation in the strength of the techniques. We caution that all these approaches are greatly improved by careful experimental design that includes adequate numbers of reference and contaminated sites and sample size. In addition, careful exposure assessment is required, including site and tissue chemistry, biomarker responses, and measures of potentially deleterious effects, such as DNA damage, or reduced reproductive output or survival. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Genetic change; Natural populations; Aquatic; Contaminants 1. Introduction 1.1. Background The merits of evaluating genetic change in aquatic organisms as a response to contaminant exposure ∗ Corresponding author. Present address: Department of Forestry and Natural Resources, 1159 Forestry, Purdue University, West Lafayelte, IN 47907, USA. Tel.: +1-765-494-3609; fax: +1-765-496-2422. E-mail address: nmbelfiore@fnr.purdue.edu (N.M. Belfiore). have been discussed for at least two decades [1,2]. Genetic approaches offer powerful tools for examining the current status of populations, inferring the history of population changes, and anticipating future population directions. Research on the effects of contaminant exposure on biological systems has historically focused on mechanisms of damage, and researchers have primarily studied test organisms ex- posed in laboratory settings. Recently, greater empha- sis is being placed on studying resident populations to relate responses in natural populations to current 1383-5742/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S1383-5742(01)00065-5