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Marine Ecology Progress Series

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MEPS 554:21-34 (2016)  -  DOI:

Estuarine consumers utilize marine, estuarine and terrestrial organic matter and provide connectivity among these food webs

Ester Dias1,2,*, Pedro Morais2,3, Anne M. Cotter4, Carlos Antunes2,5, Joel C. Hoffman4

1ICBAS—Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
2CIMAR/CIIMAR—Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal
3CCMAR—Centre of Marine Sciences, Campus de Gambelas, Universidade do Algarve, 8005-139 Faro, Portugal
4Mid-Continent Ecology Division, National Health and Environmental Effects Research Lab, US Environmental Protection Agency, 6201 Congdon Blvd, Duluth, MN 55804, USA
5Aquamuseu do Rio Minho, Parque do Castelinho s/n, 4920-290 Vila Nova de Cerveira, Portugal
*Corresponding author:

ABSTRACT: The flux of organic matter (OM) across ecosystem boundaries can influence estuarine food web dynamics and productivity. However, this process is seldom investigated taking into account all the adjacent ecosystems (e.g. ocean, river, land) and different hydrological settings (i.e. river discharge). Therefore, we aimed to quantify the contribution of autochthonous and allochthonous OM to the lower food web along the estuarine salinity gradient, under different river discharge conditions. The carbon (C) and nitrogen (N) stable isotope ratios of pelagic (zooplankton) and benthic (Corbicula fluminea) primary consumers indicated that they rely on a mixture of autochthonous and allochthonous OM, including terrestrial-derived OM. Unexpectedly, the highest contribution of terrestrial-derived OM to the estuarine food web was observed during a low river discharge period (up to 70%), that succeeded a large winter flood, showing that extreme weather events may produce prolonged effects on estuarine food webs. The contribution of marine-derived OM was higher during low river discharge periods (up to 88%) and was restricted to the seaward end of the estuary. Concomitantly, the contribution of phytoplankton to primary consumers was the highest observed (up to 91%). Further, both pelagic and benthic consumers also relied on benthic C (i.e. sediment OM and microphytobenthos). This study demonstrates that primary consumers enhance connectivity between estuarine ecosystems by utilizing subsidies of terrestrial and marine origin, and also between estuarine habitats through reliance on pelagic and benthic OM.

KEY WORDS: Allochthonous organic matter · River discharge · Pelagic · Benthic · Stable isotopes · Extreme weather events

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Cite this article as: Dias E, Morais P, Cotter AM, Antunes C, Hoffman JC (2016) Estuarine consumers utilize marine, estuarine and terrestrial organic matter and provide connectivity among these food webs. Mar Ecol Prog Ser 554:21-34.

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