Geoscience Reference
In-Depth Information
Investigators.at.various.sites.around.the.world.have.shown.via.experiments.that.
ambient.UV-B.radiation.decreases.the.hatching.success.of.some.amphibian.species.
at.natural.oviposition.sites.in.the.ield.(reviewed.in.Bancroft.et.al..2008a;.Blaustein.et.
al..1998,.2001a)..Embryos.of.some.species.are.more.resistant.to.UV-B.radiation.than.
others.(reviewed.in.Blaustein.et.al..1998;.Bancroft.et.al..2008a).
There.are.differences.in.how.species.cope.with.UV-B.radiation..For.some.spe-
cies,.in.ield.experiments,.hatching.success.is.lower.when.eggs.are.exposed.to.UV-B.
radiation.compared.with.shielded.controls..In.other.species,.hatching.success.is.not.
affected.by.UV-B.exposure.(e.g.,.Blaustein.et.al..1999;.Starnes.et.al..2000,.Häkkinen.
et.al..2001)..This.is.not.a.contradiction..Rather,.these.studies.illustrate.clear.inter-
speciic.differences.in.tolerance.to.UV-B.radiation.due.to.differences.in.molecular,.
cellular,.behavioral,.and.ecological.attributes.between.species.(Blaustein.and.Belden.
2003)..In.fact,.within.the.same.study,.conducted.at.the.same.time.and.same.site,.it.
has.been.shown.that.the.eggs.of.some.species.were.sensitive.to.UV-B,.whereas.the.
eggs.of.other.species.were.resistant.(e.g.,.Blaustein.et.al..1994a;.Anzalone.et.al..1998;.
Lizana.and.Pedraza.1998).
Importantly,. even. though. hatching. rates. of. some. species. may. appear. unaf-
fected.by.ambient.UV-B.radiation.in.ield.experiments,.an.increasing.number.of.
studies.illustrate.a.variety.of.sublethal.effects.due.to.UV.exposure..For.example,.
when. exposed. to. UV-B. radiation,. amphibians. may. change. their. behavior. (Nagl.
and. Hofer. 1997;. Blaustein. et. al.. 2000;. Kats. et. al.. 2000),. growth. and. develop-
ment. may. be. slowed. (e.g.,. Belden. et. al.. 2000;. Pahkala. et. al.. 2000,. 2001;. Smith.
et.al..2000),.or.a.number.of.developmental.and.physiological.malformations.may.
occur.(e.g.,.Worrest.and.Kimeldorf.1976;.Hays.et.al..1996;.Blaustein.et.al..1997;.
Bruggeman.et.al..1998;.Fite.et.al..1998).(recently.reviewed.by.Croteau.et.al..2008)..
Sublethal. effects. may. become. evident. even. in. species. whose. embryos. appeared.
to.be.resistant.to.UV-B.radiation.in.ield.experiments..Moreover,.numerous.ield.
and. laboratory. experiments. have. also. shown. that. UV-B. radiation. interacts. syn-
ergistically. with. a. variety. of. chemicals,. low. pH,. and. pathogens. (Kiesecker. and.
Blaustein.1995;.Long.et.al..1995;.Blaustein.et.al..2001a;.reviewed.by.Bancroft.et.
al..2008a).
The.experimental.ield.study.in.Oregon.by.Kiesecker.et.al..(2001).discussed.above.
illustrates.complex.interactions.among.precipitation-climate.change,.UV.radiation,.
and. amphibian. population. declines,. and. parallels. the. tropical. study. by. Pounds. et.
al.. (1999).. Merilä. et. al.. (2000). present. an. interesting. scenario. combining. climate.
change,.UV.radiation,.and.amphibian.breeding..They.suggest.that.if.amphibians.are.
breeding. earlier. in. northern. ecosystems. as. suggested,. as. discussed. earlier. in. this.
chapter,.then.their.annual.life.cycle.will.not.only.start.earlier.relative.to.the.calen-
dar.date.but.also.with.regard.to.maximum.UV-B.exposure..UV-B.exposure.would.
be.lower.than.if.amphibians.bred.later.in.the.spring..Thus,.they.suggest.that.global.
warming,.which.may.induce.amphibians.to.breed.earlier,.may.counteract.the.effects.
of.increasing.UV-B.levels.generated.by.a.thinning.ozone.layer.
Recent.studies.suggest.that.temperature.and.UV-B.may.interact.synergistically..
Searle. et. al. (2010). found. reduced. survival. in. larval. amphibians. exposed. to. UV-B.
radiation. in. colder. temperatures.. Van. Uitregt. et. al.. (2007). also. observed. reduced.
survival,.growth,.and.performance.when.amphibian.larvae.were.exposed.to.UV-B.
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