This chapter presents an overview of anthropogenic effects on marine biodiversity: exploitation; pollution; nutrient enrichment and eutrophication; oxygen depletion; species introduction and invasion; reduction in stratospheric ozone; tourism and extinction. In the marine realm, the introduction of the green alga Caulerpa taxifolia in 1984 by an aquarium in Monaco and its subsequent invasion had severe consequences on native Mediterranean biodiversity. Aquaculture refers to the raising of aquatic organisms such as fish, molluscs, crustaceans and aquatic plants in controlled conditions. Aquaculture of milkfish, shrimp and tuna needs larvae caught in the field and not reared in a hatchery. The non-genetic influence of the female fish on offspring performance has been termed the maternal effect. Fishing activities also have strong indirect consequences on benthic ecosystems through destruction by bottom trawling. Global warming is expected to reinforce both seasonal and permanent thermoclines, reduce mixing and thereby the quantity of nutrients available for primary production.