Toxicity and Bioavailability of Heavy Metals and Hydrocarbons in Mangrove Wetlands and Their Remediation - Environmental Contamination: Health Risks and Ecological Restoration - page 380

metal,. and. oil. pollution,. has. been. extensively. conducted. by. our. group. (Ye.
and. Tam. 2002,. 2007,. Ye. et. al.. 2003,. 2005,. Zhang. et. al.. 2007a,. Ke. et. al.. 2010).
and.others.(e.g.,.MacFarlane.and.Burchett.2001,.Qin.et.al..2007,.Zhang.et.al..
2007b).. Most. of. these. studies. have. focused. on. the. biochemical. responses.
in.plants.subjected.to.long-term,.chronic.exposure.(in.months),.which.may.
not.accurately.relect.the.rapid.response.feature.of.the.antioxidative.system..
Yan.and.Tam.(2010).investigated.the.temporal.changes.(in.the.scale.of.days).
in. the. contents. of. phenolic. compounds. and. activities. of. SOD. and. POD. in.
K. obovata .as.well.as.plant.metal.accumulation.after.exposure.to.Pb.and.Mn.
stress. and. found. that. both. stress. time. and. stress. intensity. had. signiicant.
effects,. with. signiicant. accumulation. of. Pb. and. Mn. in. the. root. on. Day. 1.
under.moderate.and.high.metal.stress;.however,.metal.accumulation.in.the.
leaf.was.only.found.on.Day.7..Metal.stress.had.no.signiicant.effect.on.TP.and.
ECT.contents.in.roots.and.leaves.on.Day.1;.however,.a.prolonged.exposure.
to.metals.caused.signiicant.decreases.in.root.TP.and.ECT;.however,.a.sub-
stantial.decease.was.observed.on.Days.7.and.49..In.contrast,.POD.activities.
in.both.roots.and.leaves.were.signiicantly.decreased.from.Day.0.to.Day.1,.
but.increased.thereafter..The.enhancement.effect.was.tissue,.metal.species,.
and. concentration. dependent.. SOD. activities. followed. a. trend. similar. to.
that.of.POD..This.study.also.revealed.that.antioxidative.enzyme.activities.in.
K. obovata .seedlings.were.more.sensitive.to.Pb.or.Mn.stress.than.the.changes.
in.phenolic.compounds.
Research. on. the. physiological. and. biochemical. responses. of. mangrove.
plants.to.toxic,.organic.pollutants.is.relatively.scarce.and.is.focused.mostly.
on.petroleum.hydrocarbons..Ke.et.al..(2010).compared.the.tolerance.of.four.
dominant.mangrove.species.in.South.China.to.different.doses.of.spent.lubri-
cating.oil..Based.on.the.mortality.rates,. B. gymnorrhiza .presented.the.highest.
tolerance.to.oil.pollution.(mortality.16.7%.at.15.L/m 2 .oil,.n.=.12.for.all.species),.
followed. by. Acanthus ilicifolius . (25%. at. 10.L. /m 2 ). and. Aegiceras corniculatum .
(83.3%.at.10.L/m 2 ),.and. K. obovata .(91.7%.at.10.L/m 2 ).was.the.most.oil-sensitive.
species.. Biochemical. responses,. including. MDA. content,. SOD. activity,. and.
O 2 − .release,.in.the.oil-treated.seedlings.of.all.species.were.enhanced.with.oil.
doses.. Zhang. et. al.. (2007a). showed. that. fresh. and. spent. lubricating. oil. at. a.
single.initial.dose.of.5.L/m 2 .posed.an.oxidative.stress.to. B. gymnorrhiza ,.lead-
ing.to.signiicant.increases.in. O 2 − .release.and.MDA.content..Spent.lubricating.
oil,.even.at.this.low.dose,.was.found.to.decrease.the.content.of.chlorophyll.
and. carotenoid,. the. activity. of. nitrate. reductase,. POD,. and. SOD,. but. it. was.
found.that.it.increased.the.MDA.content.too;.these.responses.relected.that.
A. marina .was.more.sensitive.to.spent.lubricating.oil.than. Aegiceras cornicu-
latum . whereas. canopy. oiling. resulted. in. more. direct. physical. damage. and.
stronger.lethal.effects.than.base.oiling.(Ye.and.Tam.2007)..The.most.tolerant.
mangrove.species.to.heavy.metals,. B. gymnorrhiza ,.was.also.found.to.be.the.
most.tolerant.to.spent-oil.pollution..However,.further.research.is.needed.to.
ascertain.whether.the.effect.of.oil.on.root.anatomy.and.the.oil.tolerance.mech-
anism.of.this.species.is.similar.to.the.effect.caused.by.heavy.metal.pollution.