Geoscience Reference
In-Depth Information
e.g.,.peracarid.crustaceans,.which.are.an.important.component.of.sandy.beach.mac-
rofauna.(McLachlan.and.Brown.2006)..Narrow-range.endemic.species.would.be.at.
particular. risk.. For. example,. in. southeast. Australia,. 3.7%. of. coastal. marine. inver-
tebrates. are. endemic. to. the. region. and. some. are. limited. to. cool-temperate. waters.
(O'Hara.2002)..At.even.greater.risk.would.be.the.species.unable.to.migrate.to.cooler.
waters. such. as. those. endemic. to. southeastern. Tasmania. (Edgar. et. al.. 1997).. Such.
species.may.become.extinct.as.predicted.for.terrestrial.species.in.equivalent.circum-
stances.(Hughes.2003)..Consequently,.the.distributional.effects.of.higher.tempera-
tures.may.vary.with.latitude.and.dispersive.ability.
While. some. ecosystems. have. already. experienced. substantial. temperature-
related.changes.(Walther.et.al..2002;.Hughes.2003),.the.effects.of.temperature.rise.
on. sandy. beaches. may. be. “subtle. rather. than. dramatic”. (Brown. and. McLachlan.
2002,
.
p..71).because.water.temperatures.will.rise.less.than.the.air,.many.species.
can.burrow.to.evade.extreme.heat,.and.the.change.may.be.suficiently.gradual.to.
allow.acclimation..However,.ecological.processes.such.as.photosynthesis,.decom-
position,.and.nutrient.recycling.will.probably.be.accelerated.by.temperature.rises.
as.a.product.of.the.Q
10
.law..This.would.enhance.productivity,.which,.in.turn,.may.
permit. larger. populations. and. greater. species. richness.. Alternatively,. the. faster.
decomposition.of.beach.wrack.may.enhance.the.deoxygenation.of.the.underlying.
sand.with.deleterious.effects.on.some.species..In.addition,.reproductive.processes.
may.be.affected..For.example,.the.sex.ratio.in.the.painted.turtle.(
Chrysemys picta
).
is.temperature.dependent.and.a.rise.of.2-4°C.may.compromise.the.production.of.
male.offspring.(Janzen.1994).
To.complicate.matters,.the.ecological.effects.of.temperature.change.may.be.both.
direct.and.indirect.with.modulation.from.species'.interactions..For.example,.temper-
ature.can.have.not.only.direct.effects.on.the.survival.of.intertidal.barnacles,.but.also.
indirectly.change.competitive.and.predatory.relationships.(Poloczanska.et.al..2008)..
Other.indirect.effects.of.temperature.change.on.the.beach.biota.involve.the.plank-
ton.and.oxygen..For.example,.a.rise.of.0.6°C.was.associated.with.major.changes.in.
planktonic. ecosystems. in. the. North. Sea. (Richardson. and. Schoeman. 2004).. Given.
that.plankton.is.a.source.of.food.for.some.adult.beach.species.and/or.their.larvae,.it.
is.likely.that.the.beach.biota.will.be.affected.by.planktonic.changes..Also,.increased.
water. temperatures. will. depress. dissolved. oxygen. tensions—a. factor. likely. to. be.
inluential. in. some. demersal,. stratiied. situations. (Kennedy. et. al.. 2002).. However,.
this.is.less.likely.in.the.energetic,.wave-driven.intertidal.habitat.
Finally,. temperature. can. affect. species. interactions. in. food. webs. (Kennedy. et.
al..2002)..For.example,.if.warming.and.storms.generate.more.stranded.macrophyte.
wrack,. cascading. effects. on. the. wrack-dependent. fauna. are. likely. (Dugan. et. al..
2003).. Such. effects. apparently. occurred. on. Californian. rocky. coasts. where. com-
munity.changes.were.driven.largely.by.changes.in.abundance.of.several.key.species,.
especially.habitat-forming.algae.(Schiel.et.al..2004).
s
ea
l
eVel
Global. sea. levels. were. estimated. to. rise. between. 18. and. 59. centimeters. by. 2100.
(IPCC. 2007),. but. more. recent. predictions. claim. rises. of. at. least. one. meter. per.
