HR: 13:45h
AN: NB23D-02    [Abstracts]
TI: δ¹⁵N-Size Relationships in River Invertebrate Communities: An Integrated Measure of Food web Structure?
AU: * Anderson, C
EM: Caroline_Anderson@uqtr.ca
AF: Universite du Quebec a Trois-Rivieres, Departement de Chimie-Biologie, C.P. 500, Trois-Rivieres, QC G9A5H7 Canada
AU: Cabana, G
EM: Gilbert_Cabana@uqtr.ca
AF: Universite du Quebec a Trois-Rivieres, Departement de Chimie-Biologie, C.P. 500, Trois-Rivieres, QC G9A5H7 Canada
AB: Anthropogenic perturbations can alter the composition and structure of benthic communities in rivers. Here, we examine the use of estimates of fish trophic position measured with stable nitrogen isotope ratios (δ¹⁵N), and δ¹⁵N-size relationships for the invertebrate community, as indicators of food web structure in rivers affected by various anthropogenic disturbances. Results revealed that δ¹⁵N-size relationships of invertebrate communities showed a variety of responses, some sites (50%) showing significant increases in δ¹⁵N with invertebrate size, whereas others did not. Similarly, the number of trophic levels between invertebrate-eating fish and primary consumers varied greatly among study sites, ranging from 0.6 to 2.2 levels. To investigate whether these estimates of fish trophic position integrated changes in invertebrate community structure, we compared slopes of invertebrate δ¹⁵N versus size with slopes of baseline-corrected fish δ¹⁵N versus size. Both slopes tended to be correlated, although the relationship was not significant (r² = 0.26, p = 0.07). This trend suggests, however, that invertebrate-feeding fish trophic position measured with δ¹⁵N might reflect overall community structure, and could possibly be used as an easily measured indicator of food chain collapse following anthropogenic perturbations.
DE: 1803 Anthropogenic effects
DE: 1845 Limnology
DE: 9901 NABS Student Award - Basic Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly