The main sources of eutrofizao are the activities industrial, domestic human beings and agricultural for example, the used fertilizers in the plantations can flow off superficially or be become fluid and be infiltrated in underground waters and be dragged until the mentioned water bodies. To the fast seaweed increase related with the accumulation of nutrients derived from nitrogen (nitrates), of the match, fosfatos, of sulphur, sulfatos, but also of potassium, calcium and magnesium, of – the name of bloom giving itself a blue-esverdeada, red or brownish coloration to the water, consonant the seaweed species favored for the situation. These substances are the main nutrients of fitoplncton that if it can reproduce in great amounts, becoming the esverdeada or brownish water. When these seaweed and zooplncton that of them if it feeds starts to die, its decomposition can become that poor water mass in oxygen, provoking the death of fish and other animals and the formation of toxic gases or of I smell ackward. Moreover, some seaweed species produce toxins that contaminate the drinking waters sources.

In short, many ecological effect can appear of the eutroficao, but the three main ecological impacts are: toxic loss of biodiversity, alterations in the composition of the species invasion of other species and effect. Two factors are determinative for the occurrence of full in urban areas: the waterproofing of the ground and the ambient disequilibrium provoked by the global heating. With more tarred areas, the water of rain is not absorbed by the ground and if it accumulates in the streets, transforming cities into rivers. The problem, however, is aggravated by the effect studies that it provokes the disproportionate heating of waters of the oceans and, consequentemente, more rains in determined regions of the planet? the same time where it promotes serious periods of droughts in others. 4,3 ILLNESSES CAUSED FOR INGESTAO OF WATER CONTAMINATED FOR AGROTXICO the agrotxicos, for being a material cancergenos, provoke vary degenerative illnesses, being that the main symptoms are: the arterial hipertenso, cardiovascular illnesses, fatigue and loss of heart.