MEPS 489:29-42 (2013)  -  doi:10.3354/meps10400

Stable isotopes reveal temporal and between-habitat changes in trophic pathways in a southwestern Atlantic estuary

Marlucy Coelho Claudino1,2,*, Paulo César Abreu2, Alexandre Miranda Garcia2

1Biological Oceanography Graduate Program and 2Institute of Oceanography, Federal University of Rio Grande (FURG), Avenida Itália km 8, Carreiros, CEP 96201-900, Rio Grande-RS, Brazil

ABSTRACT: Studies on food web structure in estuaries based on stable isotopes have usually not taken spatiotemporal variations in the isotopic variability of food web components into account. We investigated temporal and between-habitat variations in the isotopic composition (13C/12C and 15N/14N) of basal food sources—i.e. primary producers, particulate organic matter (POM) in the sediment or in suspension, and biofilm—and consumers and explored their implications for food web structure and dynamics. Samples of 9 basal sources (N = 224) and 6 representative invertebrates and fish (N = 303) were collected monthly over 1 yr in a marsh creek and a mudflat of the Patos Lagoon, a large southwestern Atlantic estuary. The relative contributions of food sources to consumers were estimated by mixing models. Overall, δ13C values of food sources and consumers were higher (p < 0.05) in the mudflat, whereas δ15N values were enriched (p < 0.05) in the marsh creek for most primary producers and consumers. C and N isotope values varied on both monthly and seasonal scales, with several food sources and consumers exhibiting higher values (p < 0.05) during the spring and summer. The primary food sources were POM in the sediment, C4 plants (e.g. widgeon grass), and, to a lesser extent, suspended POM. Biofilm and macroalgae were also food sources for consumers in the marsh creek and mudflat, respectively, especially during warmer seasons. Our findings corroborate the hypothesis that the Patos lagoon food web is spatially structured and supported by local basal sources and detritus of different origins, which can be seasonally important for consumers in each particular habitat.

KEY WORDS: Estuarine food web · Salt marsh detritus · Mixing model · SIAR · Widgeon grass · Biofilm · Fish · Decapod crustaceans · Temporal variability

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Cite this article as: Claudino MC, Abreu PC, Garcia AM (2013) Stable isotopes reveal temporal and between-habitat changes in trophic pathways in a southwestern Atlantic estuary. Mar Ecol Prog Ser 489:29-42

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