Toxicity and Bioavailability of Heavy Metals and Hydrocarbons in Mangrove Wetlands and Their Remediation - Environmental Contamination: Health Risks and Ecological Restoration - page 383

increasing. published. evidence. that. mangrove. sediments. are. high. in. the.
diversity.of.hydrocarbon-degrading.bacteria.as.well.as.the.genetic.diversity.
of.dioxygenase.genes.and.have.a.high.potential.of.intrinsic.bioremediation.
of.hydrocarbons.(e.g.,.Tam.et.al..2002,.2003,.Guo.et.al..2005,.2010,.Yu.et.al..
2005a,b,.Zhou.et.al..2008,.2009)..A.total.of.11.PAH-degrading.strains,.belong-
ing.to.4.genera,. Mycobacterium ,. Sphingomonas ,. Terrabacter ,.and. Rhodococcus ,.
were. isolated. from. surface. mangrove. sediments. in. South. China. (Zhou.
et. al.. 2008).. Despite. the. presence. of. the. degraders. in. contaminated. sedi-
ment,. natural. attenuation. of. hydrocarbons. such. as. PAHs. by. indigenous.
microorganisms.was.often.low,.unless.the.environmental.conditions.were.
modiied.. Bioaugmentation,. with. the. inoculation. of. isolates. with. known.
biodegradation.ability,.is.often.used.to.enhance.the.eficiency.of.bioreme-
diation..The.signiicant.enhancement.effects.of. Sphingomonas .sp.,.a.bacterial.
strain. isolated. from. surface. mangrove. sediment. to. degrade. a. three-ring.
PAH,.phenanthrene.(PHE),.in.contaminated.sediment.slurry.was.reported.
by.Chen.et.al..(2008b;.see.Figure.17.5).

30

Experiment 5

Experiment 2

6

20

4

10

2

0

0

0 24 48 72

Time (h)

96 120 144

0 24 48 72 96 120 144

Time (h)

40

Experiment 13

Experiment 11

60

30

40

20

20

10

0 0

0 24 48 72 96 120 144 0 24 48 72 96 120 144

Time (h) Time (h)

FIGURE 17.5
Effects.of.bioaugmentation.of. Sphingomonas .sp..on.phenanthrene.(PHE).degradation.in.sedi-
ment.slurry..Different.initial.PHE.concentrations.are.shown..Curves.itted.to.the.irst-order-rate.
models. indicate. that. the. rates. of. degradation. in. the. inoculated. system. were. signiicantly.
higher.than.in.the.corresponding.control.system.(◽:.inoculated.system.[dotted.line],.⚪:.control.
system.[dash.line];.mean.and.standard.deviation.of.three.replicates.are.shown)..(Adapted.from.
Chen,.J..et.al.,. Mar. Pollut. Bull .,.57,.695,.2008b.)