Salmon fertilise streamside plants

Posted on December 15, 2009

The upstream spawning migrations of North American salmon provide an important pathway for the transfer of nutrients from the sea to freshwater and terrestrial ecosystems.  In salmon streams, up to a third of the nitrogen in the leaves of streamside plants derives from migrating fish.  Several mechanisms seem to be involved in the transfer of salmon nutrients.  Floods deposit salmon carcasses on the banks of streams, and live salmon are caught by bears and other predators.  Ammonia, which is the main waste product of fish, builds up in stream water with the arrival of returning salmon.   The ammonia is converted to nitrate,   enters the water flow system below the stream bed, and it is taken up by riparian plants.  In experiments, nitrate in the subsurface flow system was quickly removed by plants and microbes.  Only a small proportion of the nitrate was lost through conversion to nitrite.

Reference:  Pinay, G., O’Keefe, T.C., Edwards, R.T. & Naiman, R.J.  2009.  Nitrate removal in the hyporheic zone of a salmon river in Alaska.  River Research & Applications 25, 367-375.