Eutrophication of the sea
Oxygen, light and mineral substances are very important for the sea, as they allow organisms to develop. These nutrients melt into the water and their excessive presence makes the sea particularly rich in organisms. In fact the result is an intense growth of algae and aquatic plants that develop rapidly, altering the balance of the ecosystem. Herbivores that eat algae and plants are not enough and do not manage to control these vegetal populations, that form a large quantity of decomposing material as they die. The decomposition and fermentation of dead organisms means consumption of oxygen, which is less and less available in the environment for those organisms that need it to survive. As a consequence the number of organisms drastically drops. This situation might occur in the Adriatic sea, where the Po river waters collect the agricultural, industrial and urban waste coming from the plain of the Po. These polluted waters are rich in nutrients and in the summer of 1989 a phenomenon of euthrophication occurred in the Adriatic sea, which was largely covered by a layer of mucilage produced by unusually growing algae.