Trophic structure of three streams with contrasting riparian vegetation and geomorphology

Citation
L. Maridet et al., Trophic structure of three streams with contrasting riparian vegetation and geomorphology, ARCH HYDROB, 144(1), 1998, pp. 61-85
Citations number
66
Categorie Soggetti
Aquatic Sciences
Journal title
ARCHIV FUR HYDROBIOLOGIE
ISSN journal
00039136 → ACNP
Volume
144
Issue
1
Year of publication
1998
Pages
61 - 85
Database
ISI
SICI code
0003-9136(199812)144:1<61:TSOTSW>2.0.ZU;2-X
Abstract
The relative influence of riparian vegetation and geomorphology on trophic structure was examined at three streams in adjacent catchments of the Frenc h Massif Central mountains. The study sites differed mainly by the degree o f anthropogenic alteration of riparian and watershed vegetation, and by val ley geomorphology. Fishes, benthic macroinvertebrates (grouped into functio nal feeding groups: FFG), macrophytes and periphyton were sampled seasonall y between July 1991 and April 1992. At the riffle-pool (10(0) m) scale, ins tream morphological units appear to control the spatial partitioning of tro phic resources and their consumers. For example, depositional zones support ed a specialized trophic structure based on coarse organic matter consumpti on, whereas in erosional zones (subdivided into lotic and lentic units) per iphyton and fine organic matter were the main food source. At the reach-seg ment scale (10(1) to 10(2) m), valley morphology was the primary factor con trolling the stream ecosystem, but anthropogenic alteration of riparian veg etation seems to override geomorphological controls on the trophic structur e. For example, the open-canopied Triouzoune Creek (gentle plateau valley), characterized by scrapers (>60% by density) and a greater epilithic algal biomass, had a autotrophic-based structure. At this site, 20% of total fish biomass was represented by brown trout (Salmo trutta) dominated by fish <1 year old. The other two sites (Vianon and Ozange creeks), with closed cano pies but different valley geomorphologies (V-shaped moderately incised vall ey versus a gently sloping plateau valley), were characterized by detrital organic matter consumers (>50% by density) and fish communities dominated b y brown trout with high densities of age 1+ individuals. Overall. the resul ts emphasize the importance of riparian vegetation on the trophic structure of streams, especially when anthropogenic alteration of riparian vegetatio n is severe. We conclude that there is a need to better integrate riparian vegetation into European stream management practices in order to maintain t he vitality of these systems over the long-term.