Autochthonous Versus Allochthonous Resources in a Tropical Rocky Shore Trophic Web Adjacent to a Marine Riparian Area

Abstract

Marine riparian areas and coastal vegetation are essential and important to the coastal marine ecosystem, although their interactions and functions are still unknown and ignored in marine ecological studies and integrated management planning. In southeastern Brazil, allochthonous resources derived from riparian Atlantic rainforests bordering rocky shores have been observed in abundance together with the shallow subtidal rocky reef benthos. In this study, we used stable isotopes (δ13C and δ15N) to characterize the main components in a benthic trophic web on a shallow tropical rocky shore, to identify the proportional contributions of allochthonous (marine riparian vegetation—MRV) to autochthonous (phytoplankton and algae) inputs and to test which basal food resources contributed most to the marine community on the Atlantic Forest–rocky coast interface. We found eight major food resources and seventeen consumers that we classified into different groups according to their feeding habits and biology. Although the main source of basal resources in the benthic trophic web in the present study remained autochthonous, the allochthonous resources were assimilated by all consumers. MRV is thus an important resource for some primary consumers and it should be included as a potential source of basal resources in marine ecosystems adjacent to marine riparian areas.