CATENAZZI, Alessandro; Florida International University: The Ulva connection: marine resources subsidize terrestrial consumers in coastal Peru

How can terrestrial animals survive in a desert with scant primary productivity? The Peruvian coastal desert is hyper-arid, but faces one of the most productive marine ecosystems, the Peru-Chile cold current. Given the stark difference in productivity between these two adjacent ecosystems, I expected to find strong linkages connecting the terrestrial and marine food web. I investigated how marine resources are incorporated in the diet and influence the distribution of terrestrial consumers. Stomach contents from geckos (Phyllodactylus angustidigitus) and carbon and nitrogen isotopic values of geckos and other terrestrial consumers suggest that marine green algae of the genus Ulva provide energy and nutrients to the terrestrial food web. Isotopic values suggest that amphipods of the genus Orchestoidea, which feed on stranded Ulva, make marine resources available to terrestrial consumers by moving between the intertidal and supratidal zones. Orchestoidea is the most common prey item in the stomachs of geckos. The spatial distribution of geckos indicates that they depend on marine resources. Geckos are 25 times more abundant between 0 and 9 m away from shore than they are between 50 and 59 m away from shore. This study describes a unique community found at the juxtaposition of one of the richest ocean currents and one of the driest deserts in the world. It shows that it is not possible to understand the structure and dynamics of the terrestrial food web without including the effects of marine energy and nutrients.