engleski

Metals as contaminants in aquatic environment and their effects on aquatic organisms

Next to natural sources, metals are present in the environment as the result of human activities which affect the state of aquatic ecosystems. Metals occur in aquatic environment in various concentration ranges (major metals, minor metals, and trace metals), and in a number of physico-chemical forms. According to their role in living organisms metals can be classified as essential and non-essential. Essential metals are necessary for normal development, growth and functioning of all living organisms (eg. Zn is component of many enzymes ; Cu and Fe are functional parts of respiratory proteins haemocyanin and haemoglobin, respectively). Non-essential metals (Cd, Pb, Hg, Ag) are usually toxic to an organism, as well as essential metals when present internally at concentrations above the limits of cellular regulatory process. Aquatic organisms are continuously exposed to variable concentrations of metals in the water. Metal uptake by the aquatic organisms depends on the specific and various environmental conditions such as water hardness, salinity, temperature, irradiance, pH, and organic matter content, as well as on the species of an organism. High metal uptake occurs particularly in the areas which are influenced by anthropogenic heavy metal contamination. In this respect, molluscs, crustaceans, fish and other aquatic organisms, that are known to accumulate high levels of heavy metals in their tissues and yet survive in these polluted environments, are suitable as bioindicator organisms. The ability of these animals to cope with elevated metal concentrations depends on their capacity to regulate the heavy metal concentration inside the cell and to accumulate excess metal in non- toxic forms. Case studies encompassing freshwater (rivers in Croatia: Sava, Sutla and Krka, and Macedonian rivers Kriva, Zletovska and Bregalnica) and marine ecosystems (central part of Eastern coast of the Adriatic Sea) and using various bioindicator organisms (bivalves, small crustaceans, fish and fish parasites) will be presented.

bioindicator organisms ; biomarkers ; metallothionein ; differential pulse voltammetry ; inductively coupled plasma mass spectrometry

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