Mechanical abrasion and organic matter processing in an Iowa stream

• Published in: Hydrobiologia Vol. 400; pp. 179 - 186
• Main Authors: HEARD, S. B, SCHULTZ, G. A, OGDEN, C. B, GRIESEL, T. C
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.04.1999; Springer Nature B.V
• Subjects: Abrasion; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Community ecology; Creeks; Creeks & streams; Detritus; Ecological function; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; Gammarus pseudolimnaeus; Limestone; Organic matter; Plantae; Synecology; Iowa; United States; North America; America; USA, Iowa, Big Mill Creek; Crustacea; Freshwater environment; Gammarus pseudolimnaeus; Organic matter; Jackson County Iowa; Litter; Arthropoda; Saprophagous; Stream; Decomposition; Invertebrata; Amphipoda
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1023/A:1003713307849

Rates of organic matter processing are key parameters for studies of stream ecosystem function and stream community ecology. Most studies of organic matter processing in streams use leaves in leafpacks or litterbags, which are immobilized and partly shielded from contact with stones in transport and in the stream bottom. As a result, these studies may underestimate the contribution of mechanical abrasion to overall processing rate (of coarse organic detritus to fine particles). We compared leaf processing rates in litter bags with and without stones (5 cm crushed limestone ballast) in Big Mill Creek, eastern Iowa. In two of three experiments, processing was significantly more advanced in bags with stones than in bags without stones: the fraction of leaf mass reduced to small fragments (1.4-9.5 mm) was 45% and 93% higher in bags with stones. In a fourth experiment, we compared the effects of stones and shredders (Gammarus pseudolimnaeus, at near-natural densities) on fragmentation of leaves in litterbags. This experiment indicated that mechanical and biological agents of processing are roughly equally important in Big Mill Creek. Our results indicate that mechanical abrasion can be an important contributor to organic matter processing in streams. If so, it may be an important source of the finer particles used by collectors. Litterbag and leafpack experiments may underestimate total processing rates and overestimate the relative importance of processing by microbes and invertebrates.[PUBLICATION ABSTRACT]