Donor-Control of Scavenging Food Webs at the Land-Ocean Interface

Multiple hypotheses have emerged to explain the apparent paradox of high diversity of the deep-sea benthos when the environmental conditions are often predicted to inhibit rather than promote diversity. Many fundamental facets of these paradigms remain incompletely understood despite being central to understanding how deep-sea ecosystems, and more generally all ecosystems, function. Here, we examine nine major paradigms of deep-sea diversity that deserve, in our opinion, a fresh research impetus. We purposely challenge many of these ideas to generate dialogue and encourage further research. Some of the axiomatic predictions of these paradigms are: (i) the deep sea is highly diverse; (ii) stable environments reduce competition; (iii) species have finely partitioned niches; (iv) biological cropping promotes diversity; (v) disturbance controls diversity; (vi) patch mosaics structure assemblages; (vii) productivity controls diversity; (viii) recovery from disturbance is slow; and (ix) the deep sea is notoriously under-sampled. We critically examine the evidence for each of these predictions and highlight areas where knowledge gaps exist and linkages to general ecological theory should occur. We conclude each section with ideas about questions and hypotheses that may fruitfully be tackled in future projects.

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“…supply of animal carcasses to scavengers; Schlacher et al . ,b) and enhance habitat heterogeneity on a seascape level (Levin & Sibuet ).…”

Section: Deep‐sea Alpha‐ and Beta‐diversity Is Not Controlled By Distmentioning

confidence: 99%

On some hypotheses of diversity of animal life at great depths on the sea floor

2015

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“…The fauna of beaches is diverse, comprising invertebrates from many phyla, and representatives from all vertebrate classes. Although most beach invertebrates are inconspicuous, they are numerous and functionally important, rapidly processing carbon (Coupland et al ., ) and linking oceanic productivity with high‐order consumers (Bergamino et al ., ; Schlacher et al ., ). Similarly, numerous vertebrate species, many of conservation concern (e.g., turtles and seabirds), depend on beaches and dunes (Schlacher et al ., ).…”

Section: Climate Change and Sandy Beaches: What's So Interesting?mentioning

confidence: 99%

Climate‐change impacts on sandy‐beach biota: crossing a line in the sand

Schoeman

Schlacher

Defeo

2014

Global Change Biology

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Sandy ocean beaches are iconic assets that provide irreplaceable ecosystem services to society. Despite their great socioeconomic importance, beaches as ecosystems are severely under-represented in the literature on climate-change ecology. Here, we redress this imbalance by examining whether beach biota have been observed to respond to recent climate change in ways that are consistent with expectations under climate change. We base our assessments on evidence coming from case studies on beach invertebrates in South America and on sea turtles globally. Surprisingly, we find that observational evidence for climate-change responses in beach biota is more convincing for invertebrates than for highly charismatic turtles. This asymmetry is paradoxical given the better theoretical understanding of the mechanisms by which turtles are likely to respond to changes in climate. Regardless of this disparity, knowledge of the unique attributes of beach systems can complement our detection of climate-change impacts on sandy-shore invertebrates to add rigor to studies of climate-change ecology for sandy beaches. To this end, we combine theory from beach ecology and climate-change ecology to put forward a suite of predictive hypotheses regarding climate impacts on beaches and to suggest ways that these can be tested. Addressing these hypotheses could significantly advance both beach and climate-change ecology, thereby progressing understanding of how future climate change will impact coastal ecosystems more generally.

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“…Animal carcasses are fundamental resources in many food webs, supporting a diverse and abundant suite of scavengers in multiple environmental settings, including sandy beaches (Kruuk 1972, DeVault et al 2003, Wilson and Wolkovich 2011, Beasley et al 2012, Barton et al 2013, Schlacher et al 2013b). In fact, carcasses of marine animals washing up on sandy beaches are a critical input for scavengers feeding at the sea-land interface (Rose and Polis 1998).…”

Section: Introductionmentioning

confidence: 99%

“…In fact, carcasses of marine animals washing up on sandy beaches are a critical input for scavengers feeding at the sea-land interface (Rose and Polis 1998). Consumption of beach-cast marine carrion is also rapid and often complete on sandy shorelines, suggesting evolutionary pathways resulting in a pivotal role of carrion in beach food webs (Huijbers et al 2013, Schlacher et al 2013b). This makes beach ecosystems good model systems to examine broader questions in food-web ecology, particularly those involving carrion-scavenger pathways.…”

Section: Introductionmentioning

confidence: 99%

Invasive carnivores alter ecological function and enhance complementarity in scavenger assemblages on ocean beaches

Brown

Schlacher

Schoeman

et al. 2015

Ecology

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Species composition is expected to alter ecological function in assemblages if species traits differ strongly. Such effects are often large and persistent for nonnative carnivores invading islands. Alternatively, high similarity in traits within assemblages creates a degree of functional redundancy in ecosystems. Here we tested whether species turnover results in functional ecological equivalence or complementarity, and whether invasive carnivores on islands significantly alter such ecological function. The model system consisted of vertebrate scavengers (dominated by raptors) foraging on animal carcasses on ocean beaches on two Australian islands, one with and one without invasive red foxes (Vulpes vulpes). Partitioning of scavenging events among species, carcass removal rates, and detection speeds were quantified using camera traps baited with fish carcasses at the dune-beach interface. Complete segregation of temporal foraging niches between mammals (nocturnal) and birds (diurnal) reflects complementarity in carrion utilization. Conversely, functional redundancy exists within the bird guild where several species of raptors dominate carrion removal in a broadly similar way. As predicted, effects of red foxes were large. They substantially changed the nature and rate of the scavenging process in the system: (1) foxes consumed over half (55%) of all carrion available at night, compared with negligible mammalian foraging at night on the fox-free island, and (2) significant shifts in the composition of the scavenger assemblages consuming beach-cast carrion are the consequence of fox invasion at one island. Arguably, in the absence of other mammalian apex predators, the addition of red foxes creates a new dimension of functional complementarity in beach food webs. However, this functional complementarity added by foxes is neither benign nor neutral, as marine carrion subsidies to coastal red fox populations are likely to facilitate their persistence as exotic carnivores.

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Donor-Control of Scavenging Food Webs at the Land-Ocean Interface

Cited by 44 publications

References 69 publications

On some hypotheses of diversity of animal life at great depths on the sea floor

On some hypotheses of diversity of animal life at great depths on the sea floor

Climate‐change impacts on sandy‐beach biota: crossing a line in the sand

Invasive carnivores alter ecological function and enhance complementarity in scavenger assemblages on ocean beaches

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