A life-history approach to predicting the recovery of aquatic invertebratepopulations after exposure to xenobiotic chemicals

A combined empirical and theoretical study was conducted to evaluate the de gree to which an understanding of the life histories of different freshwate r invertebrate taxa could improve our ability to predict their relative rat es of recovery after a toxic perturbation. Two chemicals, cypermethrin and 3,4-dichloroaniline, were introduced separately into large freshwater tanks (mesocosms, 1.25 m diameter, 1.25 m depth) containing established freshwat er invertebrate communities. Immigration was simulated in selected mesocosm s by introducing particular taxa at predetermined intervals. For both chemi cal treatments, laboratory rank toxicity data successfully predicted the ob served relative short-term mortalities of species, whereas the: relative ti mes taken for taxa to recover from cypermethrin exposure also correlated wi th their relative susceptibilities to this compound. Crucially, a significa nt component of residual variance in rank recovery to cypermethrin was expl ained by variation in overall rates of reproduction among taxa. A simulatio n model was therefore developed to allow us to integrate the disparate info rmation on invertebrate life histories into a predictive model. This model was broadly supported, particularly for the cypermethrin exposure data, whe re observed and predicted rank recovery times were highly correlated. Overa ll, this study broadly confirms the importance of life-history characters i n governing recovery and the validity of simple modeling approaches for pre dicting recovery.