AB 20:91-100 (2014)  -  DOI: https://doi.org/10.3354/ab00544

Transport of marine-derived nutrients to subtropical freshwater food webs by juvenile mullets: a case study in southern Brazil

Mauro César Lamim Martins de Oliveira1,*, Rodrigo Ferreira Bastos2, Marlucy Coelho Claudino1, Cindy Marques Assumpção1, Alexandre Miranda Garcia1

1Laboratório de Ictiologia, Instituto de Oceanografia, Universidade Federal do Rio Grande, Caixa Postal 474, Rio Grande, Rio Grande do Sul 96203-900, Brazil
2Laboratório de Ecologia Aquática, Faculdade de Biociências (FABIO), Pontifícia Universidade Católica do Rio Grande do Sul, Caixa Postal 249, Porto Alegre, Rio Grande do Sul 90619-900, Brazil

ABSTRACT: In higher latitudes of the northern hemisphere, anadromous fishes can act as biological vectors, moving marine-derived nutrients into freshwater ecosystems during their reproductive migration. Much less information is available on the potential role of marine and estuarine-related fishes as biological vectors in subtropical latitudes. Here, we investigated whether mullet juveniles might transport marine nutrients into the freshwater food webs of coastal streams in southern Brazil (32°17’S, 52°15’W). To test this hypothesis, we analyzed the stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in 10 basal production sources and 10 consumer species, including juvenile mullets, at 3 sites (surf zone, lower stream reach, headwater reach) along a marine-freshwater gradient. Our results revealed a significant decreasing trend in δ15N and δ13C values from the sea to the freshwater sites, suggesting an importation and incorporation of marine-derived nutrients into the coastal stream. A mixing model showed a marked shift in assimilation from marine to freshwater production sources by mullet Mugil liza juveniles as they moved from the surf zone into the coastal stream (lower stream and headwater reaches). Our mixing model also indicated that material of marine origin is assimilated by freshwater predators, particularly those found at the lower stream reach. Further experimental and field work is needed to evaluate the implications of marine-derived carbon and nitrogen transport by juvenile mullets for the structure and dynamics of food webs in coastal streams.

KEY WORDS: Brazil · Food web spatial subsidies · Freshwater piscivore · Mugil liza · Sea-land connectivity · SIAR mixing models

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Cite this article as: Oliveira MCLM, Bastos RF, Claudino MC, Assumpção CM, Garcia AM (2014) Transport of marine-derived nutrients to subtropical freshwater food webs by juvenile mullets: a case study in southern Brazil. Aquat Biol 20:91-100. https://doi.org/10.3354/ab00544

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