Autochthonous vs. allochthonous organic matter ingested by a macroinvertebrate in headwater streams: Gammarus sp. as a biological probe fig: 1 tab: 3
Gayte, Xavier; Fontvieille, Dominique
published: Aug 13, 1997
ArtNo. ESP141014001002, Price: 29.00 €
In headwater streams, the quantity of settling organic matter alone cannot explain the biological productivity that develops in sediments. Its use is partly determined by its quality, which in turn is related to its origin, either autochthonous or allochthonous. The aim of the study was to find a way to estimate the origin (autochthonous or allochthonous) of the organic matter consumed by benthic macroinvertebrates in small streams (Stralher order 1). Preliminary results led to the choice of the genus Gammarus as a biological probe. The comparison of two streams with different trophic budgets during two seasons and the analysis of 700 intestinal contents show that 1) the diatom/lignin ratio is the most meaningful parameter related to the origin of settling organic matter which can be measured both in sediments and in Gammarus intestinal contents, 2) large (<10 mm) seem to selectively feed on organic matter with a low c/n ratio, 3) Gammarus preferred the autochthonous part of the sediment organic pool over the allochthonous one. This selection seemed to be similar in the two streams though benthic organic matter budgets were different.