In total, more than 400 hypoxic dead zones have been identified, and their frequency has approximately doubled each decade since the 1960s (Diaz and Rosenberg, 2008, Robertson and Vitousek, 2009). This trend may continue with the occurrence, frequency, duration and extent of oxygen depletion and harmful algal blooms in coastal zones projected to increase as rivers discharge growing amounts of nutrients into the sea (OECD, 2012a). Waterbodies contaminated with pathogens are responsible for the spread of many contagious water-borne diseases (Chapra, 1997), such as cholera, giardiasis and other intestinal infections.