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Humic substance and aquatic microbial ecology Ahn, Tae-Seok

Humic substance and aquatic microbial ecology Ahn, Tae-Seok. Introduction. v DOC and POC Most allochthonous dissolved organic carbon (DOC) and particle organic carbon (POC) in aquatic ecosystem are coming from terrestrial ecosystem v DOC From exudate (Rhizosphere)

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Humic substance and aquatic microbial ecology Ahn, Tae-Seok

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  1. Humicsubstance and aquatic microbial ecology Ahn, Tae-Seok

  2. Introduction • vDOC andPOC • Most allochthonous dissolved organic carbon (DOC) and particle organic • carbon (POC) in aquatic ecosystem are coming from terrestrial ecosystem • vDOC • From exudate (Rhizosphere) • Resultant of microbial degradation • vPOC • From debris of plant (lignin, cellulose from leaves, wooden particles) • Therefore, The characteristics of DOC and POC depend on landuse • More over Dissolved humic substances (HS) comprise 50-80 % of DOC in aquatic ecosystem (Farjalla et al, 2009)

  3. Introduction A. HS is biologically inert in aquatic ecosystem B. Ecological function of HS is related to iron, phosphate bioavailability, pH condtion and light penetration (Steinberg et al 2008) C. DOC and HS enter planktonic food web through Microbial Loop (Azam et al 1983), and are important source of energy and matter

  4. Introduction D. HS is consisted with acidic materials, so the streams and lakes with HS are acidic state E. Acidic lake (pH about 4) in Japan zooplankton is abundant, but there is no phytoplankton.

  5. Introduction Zooplankton are eating bacteria and phytoplankton Red: phytoplankton Blue: bacteria stained with DTAF These microphotographys are evidence of the MICROBIAL LOOP (Sim and Ahn, 1983)

  6. Introduction G. HS is coming from forest, low nutrient concentration Brown colored HS in stream of forest July, 2009, Forest near Bayreuth

  7. Introduction H. Another source of HS is coming from poultry waste, with high concentration of nutrient Over flow of black colored waste water form poultry June 2006, Pusan, Korea

  8. HS vs Microbial loop FISH Phytoplankton grazing Zooplankton Low pH Exudate stimulates inhibits HS Stimulates =Eutrophication grazing Energy ? P source ? Naturalsource Bacteria Energy and Nutrient supply Over growth = Saprobic state HS + N, P Waste water

  9. Methods 1. Bacterial community structure in HS conatinning stream and poultry waste water •  Total bacterial number (Invitrogen, 1998) • Community with DGGE & FISH method •  β-glucosidase & phsophatese activities (Chróst, 1989) -MUF method

  10. Methods Profiles of microbial community by DGGE Total sample DNA PCR amplicon Community Fingerprinting Samples DNA extraction PCR DGGE Phylogenetic & functional diversity Sequence analysis

  11. Methods Detection of Bacillus by fluorescent in situ hybridization (FISH) Bacillus sp. from Lake Baikal by FISH

  12. Methods 2. Role of HS in aquatic ecosystem After addition of HS containing water to natural lake water, and the change of bacterial community and activity will be analyzed Grazing behavior of Zooplankton will be defined

  13. Expected results • Microbial availability of HS • HS is source for energy and matter…. So by the changes of enzymatic activities • hypothesis : if phosphatase activity is increasing=HS would be source for phosphate • if glucosidase activity is high=HS is for energy • 2. Profile of microbial community • HS would be acting as trigger for bacterial succession = how? What is the effects?

  14. Expected results 3. Different effect of nutrient rich or poor HS to aquatic ecosystem Do Zooplankton change their grazing behavior by HS ? And nutrient is effecting for grazing behavior? If that what is the machanism?

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