Marine Organisms As Biomonitors

Abstract

Biomonitors are organisms mostly used for the quantitative determination of contaminants in the environment (see Chapter 1). The present chapter discusses mainly the employment of seaweeds, sea phanerogams and molluscs as bioindicators of heavy metal contamination, since they are the organisms of choice in most of the programmes of biological monitoring of coastal marine waters (see Water Framework Directive 2000/60 EC (WFD) [1]). Bioindicators provide an integrated view of the presence of micropollutants, and in the aquatic environment they respond only to the fraction presenting a clear ecotoxicological relevance (see Chapter 1). Among the different methodological approaches of biological monitoring of a marine ecosystem, the approach based on the bioaccumulation capacity of some chemical species, as for instance trace metals, is among the most important. This capacity is particularly present among macroalgae, sea phanerogams, molluscs, oysters, etc. These organisms can be proposed as possible bioindicators when the presence of a direct correlation between internal and environmental levels of the various metals has been verified [2]. Therefore, the chemical analysis of the tissues of such organisms represents a method for measuring the integrated bioavailability of trace metals in the marine environment over time, given their remarkable bioconcentration capacity [3–5]. Comparing the levels of metals in the organisms collected at different sites is a very useful way to gather information on the biologically available levels of inorganic contaminants in the areas under study. In general, micro and macroalgae, marine phanerogams, mussels, oysters, tellinid bivalves, polychaets and crustaceans are some of the organisms used as bioindicators of marine ecosystems [4]. Marine organisms can accumulate contaminants present in solution and in the particulate material, thus determining a variation in the level of bioaccumulation depending on the trophic level occupied. Some marine invertebrates can take contaminants from the particulate material of the sediment, especially when their physico-chemical conditions are being altered. Algae and phanerogams take contaminants in solutions and many herbivorous crustaceans reflect their concentrations. Therefore, in order to have a full picture of the bioavailability of the various pollutants of water ecosystems, it is necessary to use several kinds of WITPress_BMTA_ch004.qxd 11/26/2007 17:00 Page 81