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Using stable isotope analyses to identify allochthonous inputs to Lake Naivasha mediated via the hippopotamus gut

Research output: Contribution to journalJournal articlepeer-review

Published
<mark>Journal publication date</mark>2002
<mark>Journal</mark>Isotopes in Environmental and Health Studies
Issue number4
Volume38
Number of pages6
Pages (from-to)245-250
Publication StatusPublished
<mark>Original language</mark>English

Abstract

The hippopotamus grazes nocturnally on land and resides in water during the day. Much of the ingested material must therefore be defecated directly into the aquatic system and can thus be considered an allochthonous resource available to aquatic consumers. The utility of stable isotope analyses of carbon and nitrogen to distinguish hippo faecal matter from other potential basal resources was tested at Lake Naivasha, Kenya. Hippopotami proved faithful to a short grass diet although supplementary grazing of aquatic macrophytes was observed. The typical isotopic ratios of C4 grasses ingested were not altered substantially by gut processes, and were clearly distinct from algal and aquatic macrophyte isotopic ratios. However, marginal plants such as Cyperus papyrus exhibit C4 ratios, and so the technique is suitable only for use in localities where ‘contamination’ from such sources is negligible.