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Introduction How Rivers Run Stories Value Of A River What We Can Do
Connections of a River - Connectivity
Longitudinal: Nutrient cycling (pg 5 of 9)

Organisms in all ecosystems use and reuse nutrients. Basic chemical building blocks, such as phosphorus and nitrogen, ascend and descend the food chain as plants feed herbivores, which feed carnivores, which feed scavengers and other agents of decay. This use and reuse is called cycling.

In relatively stationary systems, such as terrestrial landscapes or lakes, nutrients tend to stay put. But in river systems, the cycling is combined with downstream transport, as many of the river's resources move with the current. This cycling combined with downstream movement has come to be known as spiraling.

Sometimes the downstream movement of nutrients is reversed. A dramatic example: the salmon that migrate, die and decompose in the upper reaches of a river system. In their upstream spawning run, the salmon move large quantities of nutrients from beyond the river's mouth upstream toward the headwaters.


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