ECOLOGY/EVOLUTION

Hidden Benefits of Spawning Salmon

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Science  19 Oct 2001:
Vol. 294, Issue 5542, pp. 479
DOI: 10.1126/science.294.5542.479b

Salmon return from the sea to the freshwater breeding grounds of their birth to spawn and die. In doing so, they import ocean-derived mineral nutrients that fertilize the riparian ecosystem. The effect of this mineral import has been quantified by Helfield and Naiman for a site in southeast Alaska. Using isotopic analysis, which can identify marine-derived elements, they find that at least one-fifth of the nitrogen (N) in the needles of Sitka spruce trees and other plants near spawning sites comes from the ocean via Pacific salmon carcasses. Growth rates of trees near spawning sites were significantly higher than in reference sites. These marine subsidies to inland ecosystems are likely to decline as Pacific salmon become increasingly rare.—AMS

Ecology82, 2403 (2001).

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