Document Detail

Variation in ecosystem function in Appalachian streams along an acidity gradient.
MedLine Citation:
PMID:  19688923     Owner:  NLM     Status:  MEDLINE    
Acidification is a widespread phenomenon that damages aquatic systems, and it has been the focus of intensive management efforts. While most management has focused on community structure as an endpoint, ecosystem function is also sensitive to acidification and important in stream health. We examined how a key ecosystem function in streams, leaf breakdown, varied along a gradient of pH resulting from acid deposition, natural conditions, and liming. We also measured how invertebrate and microbial assemblage structure and microbial function were related to altered leaf breakdown rates. Leaf breakdown rates declined more than threefold along a gradient of stream acidity from pH 6.8 to 4.9. The diversity of leaf-shredding invertebrates, bacteria, and fungi showed little response to variation in pH. The abundance of one acid-sensitive caddisfly, Lepidostoma, declined with acidification, and Lepidostoma abundance explained 37% of the variation in leaf breakdown rates among sites. Microbial respiration was suppressed along the acidity gradient, although the pattern was weaker than that for breakdown rate. In short-term laboratory incubations, microbes at acidic and circumneutral sites demonstrated adaptation to ambient pH. The activity of microbial extracellular enzymes was strongly influenced by pH. In particular, the pattern of activity of phosphatase indicated increasing P limitation of microbes with increasing acidification. Our results show that leaf breakdown is a sensitive tool for examining the response of stream function to acidification and also for defining the mechanisms that drive functional response. Future management efforts should focus on key taxa that are particularly sensitive and effective at shredding leaves and also the role of shifting acidity in mediating the availability of phosphorus to microbial films that are important for stream function.
K S Simon; M A Simon; E F Benfield
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Ecological applications : a publication of the Ecological Society of America     Volume:  19     ISSN:  1051-0761     ISO Abbreviation:  Ecol Appl     Publication Date:  2009 Jul 
Date Detail:
Created Date:  2009-08-19     Completed Date:  2009-09-25     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9889808     Medline TA:  Ecol Appl     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1147-60     Citation Subset:  IM    
School of Biology and Ecology, University of Maine, Orono, Maine 04469-5722, USA.
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MeSH Terms
Hydrogen-Ion Concentration
Invertebrates / physiology
Plant Leaves / metabolism
Population Density
Rivers / chemistry*,  microbiology

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