Potential of14N isotope enrichment to resolve ambiguities in coastal trophic relationships

Isotopic tracer additions were used in a field setting to differentially label primary producers within seagrass communities and trace the flow of nitrogen to consumers. Tracer experiments were coupled with fertilisation treatments, as the tracer was added to the system via a15N-depleted (i.e.14N-en...

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Bibliographic Details
Published in:Marine ecology. Progress series (Halstenbek) 2004-01, Vol.266, p.27-33
Main Authors: Mutchler, Troy, Sullivan, Michael J., Fry, Brian
Format: Article
Language:English
Subjects:
Algae
Epiphytes
Fertilizers
Isotopes
Isotopic labeling
Nitrogen
Nitrogen isotopes
Primary productivity
Product labeling
Sediments
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Summary:Isotopic tracer additions were used in a field setting to differentially label primary producers within seagrass communities and trace the flow of nitrogen to consumers. Tracer experiments were coupled with fertilisation treatments, as the tracer was added to the system via a15N-depleted (i.e.14N-enriched) fertiliser.15N-depleted fertiliser was added to the sediments ofHalodule wrightiibeds to target the response of the seagrass alone, while addition to the water-column targeted the response of the seagrass/epiphyte complex. After 21 d of exposure to either fertilisation strategy, epiphytes and seagrass tissues inH. wrightiibeds were strongly labeled with the tracer, but the mean δ15N value of epiphytes (–78‰) was only significantly lower than that of seagrass (–31‰) in beds exposed to water-column fertilisation. Isotopic label was also detected in individuals ofTozeuma carolinense,Farfantepenaeus aztecus, andPalaemonetes pugio. The ability to both generate differential labeling inH. wrightiiand its epiphytes and trace that label to consumers suggests that water-column fertilisation experiments incorporating15N tracers may be an excellent tool for resolving trophic relationships within aquatic communities and determining how they respond to eutrophication.
ISSN:0171-8630
1616-1599