Natural organic matter controls metal speciation and toxicity for marine organisms: a review

Heavy metals are occurring in the aquatic environment as the result of natural or anthropogenic inputs, and depending on concentration, availability and resilience time, they can differently affect the animal wellness. Numerous studies reveal that more than 99% of metals in seawater are complexed with organic ligands suggesting the major role of organic complexation on metal behavior. Moreover, the amphilic character of marine natural organic matter makes this substance a relevant medium for interactions with charged and uncharged metal molecules. Here we review mechanisms and factors that control marine organic matter composition and its interactions with metals. Organic matter–metal complexes modify metal bioavailability and, in turn, change effects on living organisms.