Effects of Pollution in Aquatic Food Chains

Abstract

Aquatic ecosystems usually receive pollutants from near industrialized and highly populated zones, through riverine inflow, discharges of sewage or other wastes or the atmosphere. The trophic webs of such ecosystems can be affected by those pollutants, with the inhabitant species manifesting different vulnerabilities for certain compounds. Pollutants can bioaccumulate when ingested at a higher rate than excreted and some can also be biomagnified if accumulated at such higher rates throughout the food chain. Biomagnifiyng substances, such as organochlorines, are usually lipophilic or, like methylmercury, have a high affinity for proteins. Other pollutants, as for example heavy metals, are mostly associated with water and usually do not biomagnify at all, though they may bioaccumulate to very high concentrations in certain organisms. Bivalve molluscs and other filter-feeders usually bioacumulate substances at higher rates because they receive pollutants from suspended particles. Top predators (fish, seabirds and mammals) in aquatic trophic chains can be affected by biomagnified compounds. In this chapter we summarize the conceptual basis of and terminology used in ecotoxicological studies and review regional investigations on the effects and modes of propagation of contaminants through the food webs in the aquatic ecosystems in Argentina.