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Marine Ecology Progress Series

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MEPS 512:23-38 (2014)  -  DOI:

Trophic structure of benthic communities in the Cabo Frio upwelling system (southeastern Brazilian shelf): a temporal study using stable isotope analysis

Thais N. Corbisier1,*, Monica A. V. Petti1, Lucy S. H. Soares1, Elizabeti Y. Muto1,3, Sandra Bromberg1, Ivan Valiela

1Instituto Oceanográfico, Universidade de São Paulo, 05508-120 São Paulo, SP, Brazil
2The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA
3Present address: Fundacentro, Rua Capote Valente 710, 05409-002, São Paulo, SP, Brazil
*Corresponding author:

ABSTRACT: In Brazil, coastal upwelling is observed in 7 areas along the southeastern/southern region and is most pronounced near Cabo Frio, Rio de Janeiro. This region is exposed to moderate seasonal Ekman-driven upwelling that brings cold water with increased nutrient levels nearshore and is more frequent and intense during the austral spring and summer, primarily due to the prevalence of northeasterly winds. Our aim was to verify the influence of this upwelling on the benthic trophic structure of the inner and outer shelf off Cabo Frio through measurements of stable nitrogen (δ15N) and carbon (δ13C) isotopes. We identified 1 main pathway of organic matter (OM) transfer from the base to the top of the food web, as observed from the tendencies of the δ13C and δ15N values. The isotopic signatures of benthic consumers exhibited temporal and spatial variability, with no interaction between them. As the result of a time lag, only consumers (mostly decapod carnivores) appeared to reflect the assimilation of 15N-depleted and 13C-enriched OM produced and deposited during strong upwelling that occurred 4 mo earlier. Therefore, the intensity and period of the upwelling phenomenon were important for detecting upwelling in benthic food webs. Lighter nitrogen and heavier carbon isotopes were found on the inner shelf. Consumers may have exploited OM of different quality on the inner and outer shelf due to differences in sediment, hydrodynamics, mineralisation and assimilation of 13C-enriched microphytobenthos. Nevertheless, 4 trophic levels were estimated in the benthic communities of the continental shelf off the Cabo Frio upwelling system, independent of period or area.

KEY WORDS: Stable isotope ratios · Food web · Benthos · Continental shelf · Upwelling · Temporal variation · SE Brazil

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Cite this article as: Corbisier TN, Petti MAV, Soares LSH, Muto EY, Bromberg S, Valiela I (2014) Trophic structure of benthic communities in the Cabo Frio upwelling system (southeastern Brazilian shelf): a temporal study using stable isotope analysis. Mar Ecol Prog Ser 512:23-38.

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