4.6 Article

δ13C and δ15N biogeographic trends in rocky intertidal communities along the coast of South Africa: Evidence of strong environmental signatures

期刊

ESTUARINE COASTAL AND SHELF SCIENCE
卷 80, 期 2, 页码 261-268

出版社

ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ecss.2008.08.005

关键词

stable isotopes; delta C-13; delta N-15; biogeography; filter feeders; diet

资金

  1. National Research Foundation (NRF)
  2. African Coelacanth Ecosystem Programme (ACEP)

向作者/读者索取更多资源

Ecosystem dynamics driven by top-down controls have been well documented in rocky intertidal communities, while the effects of bottom-up influences are comparatively poorly understood. We hypothesized that large-scale signatures of the physical environment may be identifiable along the South African coastline as it is subject to two very different current systems (Benguela and Agulhas Currents) that profoundly influence primary production and thus both food type and availability. Through stable isotope analysis, we examined biogeographic patterns in multiple trophic levels at four sites along a 1400-km stretch of South African coastline and investigated the dietary role of macroalgal-derived organic carbon in rocky intertidal communities. The general positioning of trophic groups was comparable across all sites, with animals from the same trophic levels grouping together and with a delta N-15 fractionation of 1-27% between levels. The species found at all sites demonstrated east-west delta N-15 enrichment, presumably reflecting a biogeographic shift in nitrogen sources linked to upwelling on the west coast. Filter-feeders gave particularly clear results. Using discriminant analysis, mussels could be categorized into four geographic groups based on carbon and nitrogen signatures: east coast, southeast coast, south-west coast and west coast. Barnacles and polychaetes showed similar geographic groupings to mussels, but with shifts in actual values (1% depletion in delta C-13 and 3% enrichment in delta N-15 relative to mussels). This suggests that fractionation varies between species within a trophic level. IsoSource models showed that Ulva sp. made large contributions to the diets of two microalgal grazers (Siphonaria capensis and Scutellastra granularis) and this dietary dependence increased when moving from west to east coast, along the shoreline. Additionally, IsoSource models determined that relative to phytoplankton, macroalgae accounted for upwards of 60% of suspended particulate matter sampled from the shore (SPM; delta C-13 and delta N-15) at three out of four sites and linear mixing models showed over 40% (all sites) and 50% (three sites) contribution of nearshore delta C-13 and delta N-15, respectively, to the diet of all sampled filter feeders, inferring heavy dependence on macroalgal carbon. Numerous processes influence the stable isotope composition of algae, obscuring direct links between macroalgae and their consumers. In light of this, the clarity of the biogeographic patterns of filter feeders is remarkable and demonstrates a very strong signature of the physical environment in the intertidal community. (C) 2008 Elsevier Ltd. All rights reserved.

作者

我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。

评论

主要评分

4.6
评分不足

次要评分

新颖性
-
重要性
-
科学严谨性
-
评价这篇论文

推荐

暂无数据
暂无数据