Heavy metals

Definition of heavy metals: A heavy metal is a member of an ill-defined subset of elements that exhibit metallic properties, which would mainly include the transition metals, some metalloids, lanthanides, and actinides. This is the common definition for heavy metals, other definitions can be discussed in the article

Notes

Heavy metals contain both biological essential as not biological essential metals. Biological essential heavy metals include copper (Cu), iron (Fe) and zinc (Zn). Not biological essential heavy metals include lead (Pb), mercury (Hg), cadmium (Cd) and tin (Sn). 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 can be 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.