Nematodes as Bioindicators for Soil Health Assessment

Fafeng Li

Ubiquitous 5 to 8 trophic groups Live in water films of soil pores Direct contact with pollutants Differential response to disturbance

Nematodes as bioindicators?

Advantages of Biomarkers

Sensitive---provide early signals

Easy to use

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   References

  CP Group Sensitive Tolerant  

Acrobeles 2 B √   Korthals et al. 1998

Plectus 2 B √   Korthals et al. 1996

Clarkus 4 P   √ Fiscus & Neher 2002

Tylenchulaimus 4  F   √ Fiscus & Neher 2002

Enchodelus 4 O    √ Fiscus & Neher 2002

Aporcelaimus 5 P   √ Fiscus & Neher 2002

Eumonhystera 1  B √   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

Fostoria Wastewater Treatment Plant Heavy metals: Cu, Zn, Mn, etc Metal control

Toledo Tie Site (TTS) PAH

Angola & Warehouse roads PAH control

The concentration of different PAHs in soil collected from TTS

? Nematode Survival vs. high PAH concentration

PAHs Concentration (ppm)

Phenanthrene 240.46

Fluoranthene 605.68

Pyrene 775.03

5-ring PAH 8251.42

Benzo [] pyrene 2077.55

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 Fluoranthene Phenanthrene Benzo (α) pyrene

Aphelenchus 17.92 10.70 > 8*

Acrobeloides >8 >8 3.85

Clarkus 3.85 2.61 0.57

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 p

Acrobeloides 0 a 3.98*10-4 1.56*10-5

5 a 3.55*10-4 2.64*10-5 0.0948

10 0 0.00

Aphelenchus 0 a 3.77*10-4 2.28*10-5

10a 3.66*10-4 1.40*10-5 0.8943

20a 3.12*10-4 1.97*10-5 0.1671

Effect of Cu on reproduction (# eggs) Aphelenchus

Nematode [x] (ppm) Fecundity* P

Aphelenchus 0 a 872 143

10a 983 108 0.3480

20b 474 25 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

Benzo(a)pyrene

Detection Methods

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, 2-aminofluorene

Kurelec et al. 1990

Human Benzo () pyrene-diol-epoxide Kytopoulos et al. 2001

Pike Benzo () pyreneBenzo (k) fluoranthene

Ericson et al. 2000

Perch Benzo () pyrene Ericson et al. 1999

Teleost Oil contaminants Harvey et al. 1999

Crayfish PCB, DDT Schiderman et al. 1999

DNA adduct hypotheses More DNA adducts in CP4 than CP2

nematodes 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