Abstract
Food webs near the interface of adjacent ecosystems are potentially subsidised by the flux of organic matter across system boundaries. Such subsidies, including carrion of marine provenance, are predicted to be instrumental on open-coast sandy shores where in situ productivity is low and boundaries are long and highly permeable to imports from the sea. We tested the effect of carrion supply on the structure of consumer dynamics in a beach-dune system using broad-scale, repeated additions of carcasses at the strandline of an exposed beach in eastern Australia. Carrion inputs increased the abundance of large invertebrate scavengers (ghost crabs, Ocypode spp.), a numerical response most strongly expressed by the largest size-class in the population, and likely due to aggregative behaviour in the short term. Consumption of carrion at the beach-dune interface was rapid and efficient, driven overwhelmingly by facultative avian scavengers. This guild of vertebrate scavengers comprises several species of birds of prey (sea eagles, kites), crows and gulls, which reacted strongly to concentrations of fish carrion, creating hotspots of intense scavenging activity along the shoreline. Detection of carrion effects at several trophic levels suggests that feeding links arising from carcasses shape the architecture and dynamics of food webs at the land-ocean interface.
Highlights
Fluxes of materials, energy, nutrients and organisms are a fundamental feature of many ecological boundaries [1]
Energy, nutrients and organisms are a fundamental feature of many ecological boundaries [1]. These exchanges are widespread, creating inputs of allochthonous matter that can constitute subsidies for food webs in the recipient systems [2,3]. Such subsidies are disproportionally important in ecosystems that have low in situ productivity, such as sandy beaches, arctic regions, and deserts [4,5,6]
Organic matter is imported into subsidised food webs as either plant detritus or as animal carcasses
Summary
Energy, nutrients and organisms are a fundamental feature of many ecological boundaries [1] These exchanges are widespread, creating inputs of allochthonous matter that can constitute subsidies for food webs in the recipient systems [2,3]. Animal carcasses (i.e. carrion) are an abundant and widespread resource: many ecosystems contain large numbers of dead animals that have died from non-predation events [7,8]. These rich carrion resources are exploited by a diverse and highly evolved guild of scavengers [9], giving rise to a large, but often underappreciated, scavenging pathways in food webs [10]
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