Nutrient fluxes from water to land: seabirds affect plant nutrient status on Gulf of California islands

Energy and nutrient fluxes across habitat boundaries can exert profound direct and indirect effects on the dynamics of recipient systems. Transport from land to water is common and well studied; here, we document a less recognized process, substantial flows from water to land. On hyperarid, naturally nutrient poor islands in the Gulf of California, nutrient input via seabird guano directly increases N and P concentrations up to 6-fold in soils; these nutrients enrich plants. Nutrients in a long-lived cactus, a short-lived shrub, and annuals were 1.6- to 2.4-fold greater on bird versus nonbird islands. Because plant quality affects consumer growth and reproduction, we suggest that nutrient enrichment via guano ramifies to affect the entire food web on these islands. Received: 6 April 1998 / Accepted: 6 October 1998