Heavy metals

Heavy metals contain both biological essential as not biological essential metals. Biological essential heavy metals include cadmium (Cd), iron (Fe), zinc (Zn). Not biological essential heavy metals include lead (PB), mercury (Hg), copper (Cu) and aluminum (Al). Heavy metals enter the sea usually through riverine influx, atmospheric deposition, volcanic activity and anthropogenic activities. Common anthropogenic sources of these elements are mining, melting, automobile emissions, sewage, antifouling paints,... .

When present above threshold concentrations, all heavy metals are potentially toxic. The exposure of marine organisms to toxic levels of metal contaminants can cause damage to tissue, inability to regenerate damaged tissue, growth inhibition, damage to DNA. Although most marine organisms marine organisms tend to accumulate heavy metals from the environment, they are capable to store, remove (trough feces, eggs, or molting) or detoxify (through metallothioneins) many of them.