Understanding the role of zooplankton in transfer of pollutants through trophic food webs

Zooplankton is a group of organisms of key importance in regulating patterns and mechanisms through which matter, energy and pollutants are transferred from the base to the upper levels of food webs. Even if regarded as a homogeneous compartment, in reality zooplankton is composed by organisms which differ substantially one from each other, not only in their taxonomy, but also in body size, metabolic rates and ecological roles. While heterogeneity of the zooplankton compartment has been quite well documented in basic ecological studies, it is often overlooked in ecotoxicological ones, models in particular, which are usually mainly focused on sources and on top-levels of pollution patterns, the latter being directly related to human health. Such approach where intermediate steps are poorly considered, however, may result in detection of anomalous concentrations of toxicants in top-levels of the mechanisms of biomagnification. In the present chapter, we provide evidence for the need to incorporate into ecotoxicological studies, concepts and approaches developed in zooplankton ecology, not least the fact that zooplankton is made up by two hierarchical levels, or ecological roles, of primary and secondary consumers. By applying this perspective, we are able to address mechanisms responsible for temporary mismatches and anomalies in concentration of pollutants, as a consequence of changes in space and time of these two hierarchical levels within the zooplankton community.