Muto Elizabeti Y.

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Muto
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Elizabeti Y.
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  • Article
    Trophic structure of benthic communities in the Cabo Frio upwelling system (southeastern Brazilian shelf) : a temporal study using stable isotope analysis
    (Inter-Research, 2014-10-09) Corbisier, Thais N. ; Petti, Monica A. V. ; Soares, Lucy S. H. ; Muto, Elizabeti Y. ; Bromberg, Sandra ; Valiela, Ivan
    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.
  • Article
    Seasonal variability of δ13C and δ15N of fish and squid in the Cabo Frio upwelling system of the southwestern Atlantic
    (Inter-Research, 2014-10-09) Soares, Lucy S. H. ; Muto, Elizabeti Y. ; Lopez, Juliana P. ; Clauzet, Gabriela R. V. ; Valiela, Ivan
    To determine whether shifts occurred in the food web associated with upwelling at the Brazilian western boundary South Atlantic Central Water (SACW), we measured isotopic composition (δ15N and δ13C) of 38 fish and 3 squid species from the Cabo Frio food web. Sampling was performed during the austral summer upwelling period (February 2002) and the austral winter non-upwelling period (July 2001). Mean lipid-corrected δ13 δ13Ccor) values ranged from -20.17 to -15.02‰, and mean δ15N ranged from 10.28 to 16.08‰. An analysis of covariance performed using length as a covariate provided evidence of seasonal effects on the mean fish δ13Ccor and δ15N, with higher values during the non-upwelling period than during the upwelling period. These effects are most likely related to biophysical processes that occurred 1 to 6 mo earlier. The data furnish circumstantial evidence of a link between the dynamics of the SACW and the trophic structure of Cabo Frio. The trophic level of the species of fish and squids ranged between the theoretical trophic levels of 3.6 and 5.1, but there were no discrete steps, rather a continuous gradient in isotopic values. This suggests that these food webs are unstructured and the component species have mixed diets.