Carbon and nitrogen flows through the benthic food web of a photic subtidal sandy sediment

Marine Ecology Progress Series

Karline Soetaert¹  Marguerite A. Xenopoulos¹  Carlo H. R. Heip¹  Markus Huettel¹  Jack J. Middelburg¹  Victor Evrard¹ 

关键词: Stable isotopes;    Food web;    13C;    15N;    Microphytobenthos;    Meiofauna;    Macrofauna;    Bacteria;    PLFA;   

DOI  :  10.3354/meps08770

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

ABSTRACT: Carbon and nitrogen flows within the food web of a subtidal sandy sediment were studied using stable isotope natural abundances and tracer addition. Natural abundances of ¹³C and ¹⁵N stable isotopes of the consumers and their potential benthic and pelagic resources were measured. δ¹³C data revealed that consumers did not feed on the bulk microphytobenthos (MPB) but rather were selective in their food uptake, preferring either benthic diatoms (–16‰), or benthic cyanobacteria (–20‰). MPB was labelled through a pulse-chase experiment with ¹³C-bicarbonate and ¹⁵N-nitrate. The fate of MPB was followed in the different heterotrophic compartments. Transfer of ¹³C and ¹⁵N to consumers was fast, although only a small fraction of total label was transferred to the heterotrophic compartments within the 4 d of the experiment. Heterotrophic bacteria were responsible for most of the total heterotrophic incorporation of ¹³C. Within the metazoan community, the incorporation of ¹³C by the meiofauna was more than 2-fold that of the macrofauna, despite a significantly lower biomass. The dual labelling also revealed differential feeding or assimilation strategies in meio- and macrofauna. The low ¹³C:¹⁵N ratios of the meiofauna (the smaller organisms) seemed to indicate that they preferentially assimilated N or specifically grazed on N-rich resources. However, the macrofauna (larger organisms) seemed to feed on bulk sediment, consistent with high ¹³C:¹⁵N ratios. This dual approach, which combined natural abundance and a pulse-chase addition of stable isotopes, revealed crucial information on the key role of MPB in structuring benthic communities in sandy sediments.

【 授权许可】

Unknown