Nematodes as Bioindicators for Soil Health Assessment Fafeng

Nematodes as Bioindicators for Soil Health Assessment Fafeng Li

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

Advantages of Biomarkers § Sensitive---provide early signals § Easy to use § Ecotoxicological measure

Maturity Index (Bongers 1990) 1. 2. 3. Based on life history characteristics 1. Weighted mean of the individual cp value 2. MI= [cpi x fi] / n Colonizer-persister (cp-value) 1. 1: short generation, many offspring, tolerate disturbance 2. 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, CP 4 Acrobeloides, bacterivore, CP 2 Aphelenchus, fungivore, CP 2

Available field sites n Fostoria Wastewater Treatment Plant n n n Toledo Tie Site (TTS) n n Heavy metals: Cu, Zn, Mn, etc Metal control PAH Angola & Warehouse roads n 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 (LC 50) b. development (biomass through time) c. reproduction (# & size of eggs)

Genotoxicants vs. life history characteristics Toxicity (LC 50) of PAHs (ppm) Nematodes Fluoranthene Phenanthrene Benzo (α) pyrene Aphelenchus 17. 92 10. 70 Acrobeloides >8 >8 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 0 a 3. 98*10 -4 1. 56*10 -5 Aphelenchus 5 a 10 3. 55*10 -4 2. 64*10 -5 0 0. 00 0 a 10 a 20 a 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) 0 a 10 a 20 b 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 § § Benzo(a)pyrene

Detection Methods n n 32 P 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 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 n More DNA adducts in CP 4 than CP 2 nematodes n n n 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