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Stable isotope analysis of macroinvertebrates and their food sources in a glacier stream
Author(s) -
Zah Rainer,
Burgherr Peter,
Bernasconi Stefano M.,
Uehlinger Urs
Publication year - 2001
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1046/j.1365-2427.2001.00720.x
Subject(s) - trophic level , omnivore , ecology , detritivore , invertebrate , food web , isotope analysis , floodplain , algae , organic matter , biology , stable isotope ratio , environmental science , physics , quantum mechanics , predation
1. Food sources and trophic structure of the macroinvertebrate community along a longitudinal gradient were examined in a glacier stream of the Swiss Alps (Val Roseg). Analysis of multiple stable isotopes (δ 13 C and δ 15 N) and measurement of C : N ratios were used to differentiate between allochthonous and autochthonous organic matter. 2. Although isotopic signatures of algae varied widely among sites and dates, it was possible to discriminate between allochthonous and autochthonous food sources using a site‐specific approach. 3. Dominant food sources of herbivorous invertebrates in all main channel sites were epilithic diatoms and the filamentous gold alga Hydrurus foetidus . Allochthonous organic matter was of some importance only in a groundwater‐fed stream close to the floodplain margin. 4. Seasonal changes in the δ 13 C signature of the macroinvertebrates corresponded with seasonal changes in δ 13 C of the gold alga H. foetidus . This indicated that the energy base remains autochthonous throughout the year. 5. Because of limited food sources, feeding plasticity of the invertebrate community was high. Both grazers and shredders fed predominantly on algae, whereas gatherer‐collectors seemed to be omnivorous. 6. The overall enrichment of δ 15 N was 2.25‰ ( r 2 =0.99) per trophic level. On a gradient from the glacier site to a downstream forested site trophic enrichment was constant but variation in δ 15 N within trophic levels decreased.