Energy and nutrient fluxes from rivers and streams into terrestrial food webs

Abstract

Ecologists long have been aware that there is flux of energy and nutrients from riverine systems to the surrounding terrestrial landscape and vice versa. Riparian ecotones are diverse and ecologically important. Consequently, there is substantial literature examining faunal-mediated transfers of energy and nutrients from rivers into terrestrial food webs. A wide variety of taxa has been shown to utilise riparian resources, from species specialised for existence at the aquatic–terrestrial interface to opportunistic predators and scavengers. Outputs from rivers may be influenced by productivity gradients, channel geometry and the condition of the exchange surface. Until recently, consideration of faunal-transferred, allochthonous inputs has been peripheral to other research questions. The development of general models of inter-habitat transfers, together with advances in technology, has placed questions about the ecological importance of riverine outputs squarely on the research agenda. Researchers now are investigating how aquatic subsidies influence food-web dynamics at landscape scales. However, ecologists continue to largely ignore subsidisation of terrestrial food webs by energy and nutrients from floodwaters in lowland river–floodplain systems. The dearth of information about the benefits of flooding to terrestrial consumers appears to have resulted in underestimation of the gross ecological impacts of river regulation.