Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity

<em>Abstract.</em>—Anadromous fishes such as salmonids link marine and terrestrial ecosystems in coastal watersheds of western North America. We examine here the extent of isotopic enrichment of salmon-derived nutrients in soil, vegetation, and terrestrial insects among six watersheds from coastal British Columbia that differ in the density of salmon. Results demonstrate a direct relationship between the salmon spawning density and 15N enrichment in humus soil, in riparian vegetation (<em>Tsuga heterophylla, Vaccinium parvifolium, Rubus spectabilis</em>), and in riparian insects including herbivorous and carnivorous Carabidae (<em>Pterostichus</em>, <em>Scaphinotus, Zacotus</em>). The results suggest broad cycling of salmon-derived nutrients into multiple trophic levels of terrestrial ecosystems. We also describe for the first time the detection of salmon-derived nitrogen in wood samples extracted from oldgrowth riparian conifers. This result suggests new opportunities for assessing relative nutrient transfer and salmon abundance in past centuries.