¹Laboratorio de Toxicología Acuática, Sección de Graduados e Investigación, Escuela Nacional de Ciencias Biológicas, IPN Plan de Ayala y Carpio s/n, Delegación Miguel Hidalgo, México, D.F., México, CP 11340
²Facultad de Química, Departamento de Farmacia, Universidad Autónoma del Estado de México.

*Corresponding author: mgalarm@ipn.mx

Abstract

   In order to determine the influence of the presence of one or more species in a system on Zn toxic response, acute (LC₅₀ at 72 h) and sublethal toxicity (Zn uptake kinetics, and quantification of total protein content and lipid peroxidation levels) were evaluated in three benthic organisms (Hyallela azteca, Limnodrillus hoffmeisteri and Stagnicola attenuata). They were exposed either singly or together (single or multi-species test systems) to Zn-spiked sediment from Ignacio Ramírez Reservoir. Both assays showed that Zn-spiked sediments from Ignacio Ramírez Reservoir were toxic to S. attenuata, L. hoffmeisteri and H. azteca, and that toxic response was modified according to the number of species in the system. These differences may be due to multiple factors: such as benthic bioturbation which modifies physical and chemical characteristics of sediments and affects the fate and partitioning of sediment-bond contaminants, such as spiked Zn or other pollutants in sediments from Ignacio Ramírez Reservoir. In addition, the presence of more than one species in the system may lead to microenvironmental changes (pH, temperature, and organic matter and metabolic waste content), which can also contribute to toxic response differences. Also, particular characteristics of each of the species involved in the study became evident. The snail and amphipod are facultative benthic organisms, while the worm is obligate. Such way of life differences may have modified the bioavailability of contaminants, determining their toxicity.