Phytoplankton and macrophyte contributions to littoral food webs in the Galician upwelling estimated from stable isotopes

The natural abundance of stable carbon and nitrogen isotopes was analysed in plankton and intertidal benthos at coastal sites of Galicia (NW Spain) to determine the relative importance of phytoplankton versus benthic macrophytes, and marine versus anthropogenic nutrients, in supporting littoral food...

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Bibliographic Details
Published in:Marine ecology. Progress series (Halstenbek) 2006-08, Vol.318, p.89-102
Main Authors: Bode, Antonio, Alvarez-Ossorio, Maria Teresa, Varela, Manuel
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
Diet
Food webs
Fundamental and applied biological sciences. Psychology
Macrophytes
Marine
Marine ecosystems
Nitrogen
Nitrogen isotopes
Nutrients
Phytoplankton
Primary productivity
Sea water ecosystems
Synecology
Upwelling water
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Summary:The natural abundance of stable carbon and nitrogen isotopes was analysed in plankton and intertidal benthos at coastal sites of Galicia (NW Spain) to determine the relative importance of phytoplankton versus benthic macrophytes, and marine versus anthropogenic nutrients, in supporting littoral food webs in this upwelling ecosystem. Phytoplankton was significantly less enriched in heavy isotopes than most macrophytes (seagrasses and 3 classes of macroalgae). Nitrogen isotopes showed significant enrichment of primary consumers (zooplankton, benthic suspension feeders and deposit feeders) relative to primary producers. The average enrichment between trophic levels, however, was low (Δδ13C = +0.1 ‰, Δδ15N = +1.4 ‰), suggesting the prevalence of omnivory. The use of marine nitrogen was inferred from the low nitrogen isotope abundance values of phytoplankton and rhodophycea. In contrast, phaeophycea and chlorophycea displayed high nitrogen isotope enrichment, particularly at sheltered sites, suggesting the influence of anthropogenic nitrogen. The diets of benthic consumers reflected the local diversity of available sources, with a large influence of phytoplankton and marine nitrogen at open sea sites. Average contributions of phytoplankton to diet always exceeded 40% in the case of suspension feeders but were generally
ISSN:0171-8630
1616-1599
DOI:10.3354/meps318089