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Analysis of the variation of stable carbon isotopes in macroalgae communities from shallow marine habitats in the Gulf of California ecoregion
  • MARTIN F Soto-Jimenez,
  • Roberto Velázquez-Ochoa,
  • Maria Julia Ochoa Izaguirre
MARTIN F Soto-Jimenez

Corresponding Author:martin@ola.icmyl.unam.mx

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Roberto Velázquez-Ochoa
Universidad Nacional Autonoma de Mexico
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Maria Julia Ochoa Izaguirre
Universidad Autonoma de Sinaloa
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The C isotopic composition in macroalgae (δ13C) is highly variable and its prediction is very complex relative to terrestrial plants. To contribute to the knowledge on the variations and determinants of δ13C-macroalgal, we analyzed a large stock of specimens varying in taxa and morphology and inhabiting shallow marine habitats from the Gulf of California Ecoregion featured by distinctive environmental conditions. A large δ13C variability (-34.61‰ to -2.19‰) was observed, mostly explained on the life form (taxonomy, morphology and structural organization), and modulated by the interaction between habitat features and environmental conditions. The intertidal zone specimens had less negative d13C values than in subtidal zone. Except pH, environmental conditions of the seawater do not contribute to the δ13C variability. Specimens of the same taxa showed δ13C similar patterns, to increase or decrease, with latitude (21º-30°N). d13C-macroalgal provides information on the inorganic carbon source used for photosynthesis (CO2 diffusive entry vs HCO3- active uptake). Most species showed a δ13C belong into a range that indicates a mix of CO2 and HCO3- uptake; the HCO3- uptake by active transport is widespread among GCE macroalgae. About 20-34% species depending on cutoff limits for CCM presence showed at least one specimen with δ13C>-10‰, suggesting that potentially could have highly efficient CCM. Ochrophyta presented a high number of species with d13C>-10‰, suggesting widespread HCO3- use by non-diffusive mechanisms. Few species belonging to Rhodophyta relied on CO2 diffusive entry (d13C<-30‰) exclusively. δ13C provides useful information about the physiological and environmental status of macroalgae.