English: A schematic showing the abundance of plankton in the oceans. The schematic was based on an image in the book "Waardeer de oceanen" by Lawrence Williams. Plankton is a fish feed giving an indication of the richness of fishspecies and their numbers in that part of the ocean. It is an ocean fertiliser natural in origin (eg unlike others as ammoniumnitrate). Its variation in abundance shows what parts of the ocean are in more need of protection. Plankton is richer near landsurfaces (trough soil runoff carrying nutrients, ...). It is especially rich near river mouths.