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Mangrove and mudflat food webs are segregated across four trophic levels, yet connected by highly mobile top predators
Marley, Guy Lawrence, Andrew Phillip, Dawn Hayden, Brian
Marley, Guy
Lawrence, Andrew
Phillip, Dawn
Hayden, Brian
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Abstract
Seascape connectivity is crucial for healthy, resilient ecosystems and fisheries. Yet,
our understanding of connectivity in turbid mangrove-lined estuaries—some of the world’s most
productive ecosystems—is limited to macrotidal systems, and rarely incorporates highly mobile
top predators. We analysed δ13C and δ15N isotope values of 7 primary producers, 24 invertebrate
taxa, 13 fishes, 4 birds and 1 reptile to reveal trophic interactions within and between a mangrove
and adjacent mudflat in a microtidal system of the Gulf of Paria, Orinoco River estuary. Primary
producers, invertebrates and fishes collected within the mangrove were significantly depleted in
13C and 15N compared to those collected on the mudflat. Stable isotope mixing models showed that
mangrove-derived carbon was predominantly assimilated by invertebrates (78 ± 5% SE) and fishes
(88 ± 11%) sampled in the mangrove. In contrast, invertebrates and fishes sampled in the mudflat
derived <21% of their carbon from mangrove sources. Instead, microphytobenthos and phytoplankton
underpinned the mudflat food web. Scarlet ibis Eudocimus ruber and yellow-crowned
night heron Nyctanassa violacea were also highly associated with mangrove carbon sources.
However, osprey Pandion haliaetus, snowy egret Egretta thula and spectacled caiman Caiman
crocodilus obtained carbon from both mangrove and mudflat sources, effectively integrating the
food webs. The present study demonstrates simultaneous aspects of food web segregation and
connectivity, as well as the importance of surveying the entire food web across a range of tidal
systems when investigating seascape connectivity.
Citation
Marley, G., Lawrence, A., Philip, D. A. & Hayden, B. (2019). Mangrove and mudflat food webs are segregated across four trophic levels, yet connected by highly mobile top predators. Marine Ecology Progress Series, 632, 13-25.
Publisher
Inter Research
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Marine Ecology Progress Series
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DOI
10.3354/meps13131
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Article
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1616-1599