Although oceans cover two-thirds of the surface of the Earth, they are surprisingly vulnerable to human influences, ＿＿（57）＿＿ overfishing, pollution from run-off, and dumping of waste. This kind of pollution can have serious economic and health impacts by killing marine life and damaging habitats and ecosystems. Toxins from pesticides, fertilizers, and other chemicals used on farms ＿＿（58）＿＿ nearby rivers that flow into the ocean, and this can cause extensive loss of marine life in bays and estuaries, ＿＿（59）＿＿ the creation of dead zones. The dumping of industrial, nuclear and other waste into oceans was legal until the early 1970's when ＿＿（60）＿＿ . However, illegal dumping still occurs in many places.