POPULATION CONSEQUENCES OF CHRONIC TOXICITY - INCORPORATING DENSITY-DEPENDENCE INTO THE ANALYSIS OF LIFE TABLE RESPONSE EXPERIMENTS

Data from chronic toxicity tests are usually analysed by calculating h ow the toxicant reduces population growth rate. The contribution of ef fects on different parts of the life history to this reduction can be determined using sensitivity analyses and life table response experime nts (LTREs). These provide a convenient descriptor of what happens wit hin the laboratory toxicity test, but are only a good predictor of lik ely consequences in the field if density dependence of population dyna mics can be ignored. Here I show how sensitivity analysis and LTREs ca n be applied to density dependent populations and illustrate the metho ds with data on the toxicity of dieldrin to Eurytemora affinis. I also outline the extension of the approach to populations which experience variations in vital rates. Stationary population sizes in density dep endent populations at equilibrium mean that vital rates late in life a re usually more important than in the density independent analysis. Su bstantial reductions in some vital rates can have little impact on the population if they are compensated by reductions in the intensity of density dependence. This represents one aspect of the assimilative cap acity of ecological systems. (C) 1998 Elsevier Science B.V.