Marine Pollution Oil spills, toxic wastes and plastics are familiar marine pollutants. However, human interaction with the ocean results in other, often more serious threats.
Pipelines usually discharge below the low water mark.
Stormwater drains collect and channel the water from all non-porous surfaces, such as pavements and tarred roads, within a catchment. Rivers carry to the sea water containing contaminants such as nutrients and pesticides from agricultural runoff, faecal pollution resulting from poor sanitation, and industrial discharges. Unlike many countries in Europe and the USA, South Africa does not dump industrial wastes or sewage sludges. Decomposition of organic matter causes a drop in dissolved oxygen, particularly in calm weather and sheltered bays. These blooms can discolour the water, clog fish gills, or even be toxic, e.g. red tides.