The trophic significance of the invasive seaweed Sargassum muticum in sandy beaches |
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| Authors: | Francesca Rossi Celia Olabarria Mónica Incera Josefina Garrido |
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| Institution: | 1. IMAR-CMA Marine and Environmental Research Centre University of Coimbra, Portugal;2. Departamento de Ecoloxía e Bioloxía Animal, Universidad de Vigo, Campus As Lagoas-Marcosende, 36310 Vigo (Pontevedra), Spain;3. Centro Tecnológico del Mar-Fundación CETMAR, C/Eduardo Cabello s/n, 36208 Bouzas-Vigo (Pontevedra), Spain;1. Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Carretera Utrera Km 1, 41013 Sevilla, Spain;2. Centro de Estudos do Mar, Departamento de Ciências da Terra, Universidade Federal do Paraná, Av. Beira Mar, s/n CEP 83255-000, Pontal do Sul, Pontal do Paraná, PR, Brazil;3. Instituto de Biologia, Departamento de Biologia Marinha, Universidade Federal Fluminense, Outeiro de São João Batista s/n, Campus do Valonguinho Centro, Niterói, CEP 24020-140 Rio de Janeiro, RJ, Brazil;4. Departamento de Zoología, Universidad de Sevilla, Av Reina Mercedes 6; 41012, Sevilla, Spain;5. Laboratório de Ecologia Bêntica, Departamento de Ciências Naturais, Universidade Federal do Estado do Rio de Janeiro, Avenida Pasteur, 458, CP 22290-240 Rio de Janeiro, RJ, Brazil;1. University of Cologne, Institute for Zoology, General Ecology, Zülpicher Str. 47b, 50674 Cologne, Germany;2. Zoological Museum Hamburg, Center of Natural History, Martin-Luther-King-Platz 3, Hamburg 20146, Germany;3. Bavarian State Collection of Zoology, Münchhausenstrasse 21, 81247 Munich, Germany;4. German Centre for Marine Biodiversity Research, Senckenberg Research Institute, Südstrand 44, 26382 Wilhelmshaven, Germany;5. GEOMAR, Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany;6. German Centre for Marine Biodiversity Research, Senckenberg Research Institute, c/o CeNak, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany;7. Ludwig-Maximilian University Munich, Biocenter, Department Biology II, Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany;8. Institute for Hydrobiology and Fisheries Research, Olbersweg 24, 22767 Hamburg, Germany |
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| Abstract: | Native and exotic seaweeds frequently lie on the beach and sustain part of the benthic food web. However, the role of exotic seaweeds as food sources for beach consumers has been poorly studied. We studied the temporal and spatial variability in the trophic significance of the invasive brown seaweed Sargassum muticum on sandy beaches. We measured the stable isotopes (δ13C and δ15N) in the tissues of S. muticum and of invertebrate consumers and estimated the dietary biomass proportion of S. muticum during four sampling dates at two beaches and heights on the shore. Samples were collected from eight pitfall traps placed at a distance of 2 m from each other. Detrital macroalgae and seagrasses were also collected by hand within an area of 30 cm around each pitfall trap. We measured the spatial and temporal variability in the isotope composition of the beach consumers and of S. muticum using different models of analyses of variance. We then calculated the biomass proportion of S. muticum to the animal diet with a two-isotopic mixing model. The invasive alga S. muticum seemed to be one of the main food sources for the amphipod Talitrus saltator and, to a less extent, for the isopod Tylos europaeus. The importance of S. muticum was however temporally variable and decreased during spring (in March and May), probably due to the availability of native macrophytes. The supply of invasive wrack to beach food webs thus deserves more attention if we want to understand their role in influencing food web dynamics. |
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