The document discusses various types of water pollution including eutrophication caused by excessive nutrients, low dissolved oxygen levels, and nitrates and phosphates. Eutrophication leads to large algal blooms which can cause oxygen sags when the algae dies off. Dissolved oxygen levels depend on factors like temperature and are important for supporting aquatic life. Excess nitrates and phosphates from sources like fertilizer runoff and sewage can cause algal blooms, low oxygen, and harm fish and other aquatic animals. The document outlines these issues as well as transportation, sewage, toxic chemicals, and heavy metals as major causes and concerns of ocean pollution.