Trace element trophic transfer in aquatic food webs

In this review I discuss the importance of the processes of trophic transfer of trace elements (TTET) in aquatic food chains and webs, and suggest some tools and strategies for their study. The ET (essential and nonessential) are trophically transferred and can accumulate up to toxic levels in organisms, populations and communities. The processes of TTET are very complex due to the many factors that affect them. The characteristic high productivity, diversity and environmental seasonality associated with subtropical coastal ecosystems, pose additional complexity to the already difficult study of such processes. Today's modern techniques and methods of study facilitate the understanding and evaluation of such processes. Among these are the stable isotopes of C and N, which are used to define the species' trophic position in an ecosystem and establish food web structures and trace energy and ET paths. There are mathematical models (e.g. kinetic accumulation model) that allow the assessment of TTET processes based on four basic mechanisms (ingestion, assimilation, excretion and growth). These mechanisms can be measured experimentally in the laboratory by using radiotracers and heavy metal's isotopes artificially enriched. The increasing pollution by, together with the simultaneous eutrophication occurring in the Mexican coasts, emphasizes the urgency to study and assess TTET processes, as well as the derived environmental and public health risks.