Transcript Nematodes as Bioindicators for Soil Health Assessment Fafeng Li

Nematodes as Bioindicators for
Soil Health Assessment
Fafeng Li
Nematodes as bioindicators?
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Ubiquitous
5 to 8 trophic groups
Live in water films of soil pores
Direct contact with pollutants
Differential response to disturbance
Advantages of Biomarkers
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Sensitive---provide early signals
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Easy to use
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Ecotoxicological measure
Maturity Index (Bongers 1990)
 Based on life history characteristics
 Weighted mean of the individual cp value
 MI= [cpi x fi] / n
 Colonizer-persister (cp-value)
 1: short generation, many offspring, tolerate
disturbance
 5: long life-cycle, few offspring and sensitive
to disturbance
 cp-value inferred based on morphology
Discrepancies between inferred nematode
CP values & reaction to environmental
disturbance
Genus
Trophic
Disturbance
CP
Group
Sensitive
Acrobeles
2
B
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Korthals et al. 1998
Plectus
2
B
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Korthals et al. 1996
Clarkus
4
P
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Fiscus & Neher
2002
Tylenchulaimus
4
F
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Fiscus & Neher
2002
Enchodelus
4
O
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Fiscus & Neher
2002
Aporcelaimus
5
P
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Fiscus & Neher
2002
Eumonhystera
1
B
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References
Tolerant
Fiscus & Neher
2002
Dissertation Proposal Objectives
1) Quantify effect of genotoxicants on life history
characteristics of nematodes
2) Identify correlation between PAH concentration
and DNA adduct formation
Experimental Plan
Chemicals:
Benzo () pyrene
Fluoranthene
Cu
Nematodes:
Clarkus, predator, CP4
Acrobeloides, bacterivore, CP2
Aphelenchus, fungivore, CP2
Available field sites
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Fostoria Wastewater Treatment Plant
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Toledo Tie Site (TTS)
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Heavy metals: Cu, Zn, Mn, etc
Metal control
PAH
Angola & Warehouse roads
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PAH control
The concentration of different PAHs in soil
collected from TTS
PAHs
Concentration (ppm)
Phenanthrene
240.46
Fluoranthene
605.68
Pyrene
775.03
5-ring PAH
8251.42
Benzo [] pyrene
2077.55
? Nematode Survival vs. high PAH
concentration
Objective 1
Quantify effect of genotoxicants on life history
characteristics of nematodes
a. survivorship (LC50)
b. development (biomass through time)
c. reproduction (# & size of eggs)
Genotoxicants vs. life history characteristics
Toxicity (LC50) of PAHs (ppm)
Nematodes
pyrene
Fluoranthene Phenanthrene Benzo (α)
Aphelenchus
17.92
10.70
Acrobeloides
>8
>8
3.85
3.85
2.61
0.57
Clarkus
> 8*
Effect of Cu on Acrobeloides
development
: 10
Effect of Cu on development of
Aphelenchus
Effect of Cu on reproduction (egg size)
Nematode
[x] (ppm) Biomass (g)  SE
Acrobeloides
0a
3.98*10-4  1.56*10-5
Aphelenchus
5a
10
3.55*10-4  2.64*10-5
0  0.00
0a
10a
20a
3.77*10-4  2.28*10-5
3.66*10-4  1.40*10-5
3.12*10-4  1.97*10-5
p
0.0948
0.8943
0.1671
Effect of Cu on reproduction (# eggs)
Aphelenchus
Nematode
Aphelenchus
[x] (ppm)
0a
10a
20b
Fecundity*
872  143
983  108
474  25
P
0.3480
0.0006
* (# eggs + # juveniles) / # adults
Conclusion: For Aphelenchus, Cu stress
reduces its fecundity, not the size of eggs.
Objective 2
Identify correlation between PAH
concentration and DNA adduct
formation
DNA adducts as biomarkers
Covalently bound to DNA
Measure of genotoxicity
PAH response
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Benzo(a)pyrene
Detection Methods
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32P
radioactive postlabeling
•degree of total covalent binding
•pollutant-specific
Enzymatic-linked immunosorbent assays
(ELISA)
• pollutant-specific
•actual degree of binding
Previous use of DNA adducts
as biomarkers
Species
Agent
Sources
Mussel
Benzo () pyrene, 2aminofluorene
Benzo () pyrene-diol-epoxide
Kurelec et al. 1990
Perch
Benzo () pyrene
Benzo (k) fluoranthene
Benzo () pyrene
Teleost
Oil contaminants
Crayfish
PCB, DDT
Ericson et al.
2000
Ericson et al.
1999
Harvey et al.
1999
Schiderman et
al. 1999
Human
Pike
Kytopoulos et al.
2001
DNA adduct hypotheses
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More DNA adducts in CP4 than CP2
nematodes
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Acute (few days to months) - lab
Chronic (many years to decades) – field
DNA adduct formation is greater in
unexposed or non-adapted population
Acknowledgements
Dr. Deborah Neher
Tom Weicht
Dr. John Plenefisch