Analysis of the variation of stable carbon isotopes in macroalgae
communities from shallow marine habitats in the Gulf of California
ecoregion
Abstract
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.