Population increase in the coastal zone results in a high amount of waste generated with concomitant pollution of the coastal and marine ecosystems. Physical alteration and destruction of habitats, nutrient over-enrichment, marine litter and untreated wastewater discharge are the four problems identified for priority action (UNEP/GPA 2006). Increased nutrient load to coastal and marine waters leads to increased phytoplankton productivity. Algae and autotrophs use up oxygen and begin to die off. Aerobic decomposers (bacteria) multiply and use up even more oxygen. As a consequence, the entire water column is devoid of oxygen (a phenomenon known as ‘hypoxia’), causing aerobic organisms (for example, fish) that rely on oxygen to die.
From collection: Sanitation and Wastewater Atlas of Africa - Ecosystems