Simultaneous analysis of δ13C, δ15N and δ34S ratios uncovers food web relationships and the trophic importance of epiphytes in an eelgrass Zostera marina community

Marine Ecology Progress Series

Ulrich Sommer¹  Agnes Mittermayr¹  Thomas Hansen¹ 

关键词: Stable isotopes;    Food web;    Seagrass;    Epiphytes;    Trophic level;   

DOI  :  10.3354/meps10569

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

ABSTRACT: Simultaneous analysis of carbon, nitrogen and sulphur stable isotope ratios was applied in this pilot study to examine the food web of a Zostera marina L. system in the western Baltic Sea. Samples of 3 potential food sources: eelgrass, epiphytic algae and seston, as well as 69 consumer species were collected during the growing season of Z. marina from March to September 2011. The measured δ¹³C values of epiphytes were close to δ¹³C values of eelgrass, impeding a clear distinction of those 2 carbon sources, whereas seston δ¹³C values were clearly different. This frequently encountered problem was solved by the additional use of δ³⁴S, which resulted in easily distinguishable values for sediment and seawater derived sulphur. The combination of δ³⁴S and δ¹³C values made a separation of carbon sources possible and enabled the allocation of potential food sources to consumers and a description of their trophic relationships. The results of stable isotope ratio analysis of this eelgrass community strongly indicate a food web based on epiphyte and seston production. δ¹⁵N values show a food web consisting of large numbers of generalists and a high degree of omnivory amongst the consumer species analysed. This implies an occupation of every trophic position possible, which is supported by an even distribution of δ¹⁵N values. Previously described eelgrass food webs may have to be re-evaluated by considering sulphur stable isotope ratios in order to provide a clear picture on primary carbon sources.

【 授权许可】

Unknown