Differential Utilization of Allochthonous and Autochthonous Inputs by Aquatic Invertebrates in Some New Zealand Streams: A Stable Carbon Isotope Study

Abstract

13C/12C ratios indicated that the faunas of small, forested streams depended primarily on allochthonous sources of C; variable utilization of allochthonus and autochthonous materials was shown by species from a grassland stream. Relatively 13C-depleted values obtained from the mayfly. Deleatidium from forested sites suggest that larvae is assimilate algae selectively. A shift to greater dependence on autochthonous energy sources was shown by invertebrates from small, recently clearcut catchments (1-4 yr) in response to canopy removal and flushing of forest-derived organic materials from the streams. Although coarse in its resolving power, stable C isotope methodology provides insights into the trophic linkages within a community and has potential as a management tool.