often help maintain coral reefs as they feed on macroalgae that competes with the coral. As this relationship is mutually beneficial, a positive feedback cycle is formed between the two organisms, making them both responsible for creating and maintaining coral reef ecosystems. Whales are also being increasingly recognised for their role as ecosystem engineers despite the loss of up to 90% of their numbers during the commercial whaling era. Whales defecate at the surface and release nutrients that boost the growth of phytoplankton. As whales migrate across the oceans, and move up and down the water column, they help to spread these nutrients in a process that is known as the "Whale Pump". See also Niche construction Structures built by animals Nest-building in primates References Bibliography External links A lecture by Moshe Shachak, the developer of the concept of ecosystem engineers (together with CG. Jones and JH. Lawton) during the 90's. Biology terminology Ecological niche Habitat Invasive species Landscape ecology Systems ecology