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Variability in nitrogen stable isotope ratios of macroalgae: consequences for the identification of nitrogen sources
Author(s) -
OchoaIzaguirre María Julia,
SotoJiménez Martín F.
Publication year - 2015
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/jpy.12250
Subject(s) - biogeochemical cycle , ecosystem , biology , water column , δ15n , environmental chemistry , nitrogen cycle , nitrification , eutrophication , stable isotope ratio , nitrogen , isotopes of nitrogen , ecology , denitrification , environmental science , δ13c , chemistry , physics , organic chemistry , quantum mechanics , nutrient
In our research, we collected and analyzed numerous macroalgal specimens (738) for isotopic analysis sampled over a year at monthly intervals across 20 sites within the U rías lagoon complex, a typical subtropical coastal ecosystem located in the G ulf of C alifornia. We quantified and characterized (chemically and isotopically) the N loads received by U rías throughout a year. We studied the spatial‐temporal variation of the chemical forms and isotopic signals of the available N in the water column, and we monitored in situ different environmental variables and other hydrodynamic parameters. Multiple N sources (e.g., atmospheric, sewage, seafood processing, agriculture and aquaculture effluents) and biogeochemical reactions related to the N cycle (e.g., ammonia volatilization, nitrification and denitrification) co‐occurring across the ecosystem, result in a mixture of chemical species and isotopic compositions of available N in the water column. Increased variability was observed in the δ 15 N values of macroalgae (0.41‰–22.67‰). Based on our results, the variation in δ 15 N was best explained by spatio‐temporal changes in available N and not necessarily related to the N sources. The variability was also explained by the differences in macroalgal biology among functional groups, species and/or individuals. Although the δ 15 N‐macroalgae technique was a useful tool to identify N sources, its application in coastal ecosystems receiving multiple N sources, with changing environmental conditions influencing biogeochemical processes, and high diversity of ephemeral macroalgal species, could be less sensitive and have less predictive power.