Food webs in forest and pasture streams in the Waikato region, New Zealand: A study based on analyses of stable isotopes of carbon and nitrogen, and fish gut contents
作者:
BrendanJ. Hicks,
期刊:
New Zealand Journal of Marine and Freshwater Research
(Taylor Available online 1997)
卷期:
Volume 31,
issue 5
页码: 651-664
ISSN:0028-8330
年代: 1997
DOI:10.1080/00288330.1997.9516796
出版商: Taylor & Francis Group
关键词: stable isotopes;carbon;nitrogen;invertebrates;fish;food webs;land use
数据来源: Taylor
摘要:
Stable isotopes of carbon (C) and nitrogen (N) were studied in 11 stream communities in the Waikato region of New Zealand. From comparisons of mean δ13C and δ15N values, food webs in the shaded, forest streams were clearly based on allochthonous material (conditioned leaf litter and terrestrial invertebrates). Autotrophs in forest streams were not a significant C source for the food webs. However, the C source of food webs in the unshaded pasture streams appeared to be a mixture of allochthonous and autochthonous material. Conditioned leaf litter appeared to contribute to the pasture stream food webs, and the δ13C and δ15N of some samples of epilithic diatoms indicated their consumption by invertebrates in pasture streams. Fish ate a wide range of aquatic invertebrates; longfinned eels (Anguilla dieffenbachii) and banded kokopu (Galaxias fasciatus) also had a large proportion of terrestrial invertebrates in their diet. Filamentous green algae were found only at pasture sites, where they were sometimes abundant. The wide range of δ13C values of filamentous green algae (‐18.8 to ‐29.7‰) complicated understanding of their role in the stream food webs. The δ13C values ofCladophorawere related to water velocity, with more13C‐enriched values in pools than in runs (‐23.2‰ in pools, mean velocity 0.12 m s−1; ‐28.1‰ in runs, mean velocity 0.24 m s−1). Crayfish and the gastropod molluscPotamopyrgusappeared to be the only invertebrates to eat filamentous green algae.
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