Geoscience Reference
In-Depth Information
Tropical and temperate calcareous algae are among the most
sensitive calcifying organisms to ocean acidification . This is due, at
least partly, to the fact that their skeleton is made up mostly of
magnesian calcite, a particularly soluble (and therefore unstable) form
of
CO
−
. Studies carried out until now have shown a negative effect
of acidification on their recruitment, survival, growth and,
unsurprisingly, their calcification rate [KUF 07, MAR 09]. It seems
that algae, as with corals, are more sensitive to acidification when it is
accompanied by an increase in temperature [DIA 12], which
could lead to significant modifications in the structure and function
of benthic communities dominated by these organisms in the
coming decades. Due to their abundance, ecological importance and
key contributors of carbonate deposits (and therefore habitat creation),
the vulnerability of corals and calcareous algae to the increase of
pCO
2
would probably have major consequences on coastal
ecosystems.
3
5.4.1.2.3. Mollusks
Like corals and calcareous algae, benthic mollusks also provide
important ecological services. They regulate the flow of energy and
nutrients in coastal ecosystems, offering a habitat for numerous
benthic organisms and represent an important source of food for birds.
They also have a non-negligible market value and participate in the
economy of many coastal regions. Shellfish aquaculture has increased
by close to 8% per year over the course of the last 30 years, to create a
market of more than 13.1 billion US dollars in 2008 [FAO 09]. The
vast majority of mollusks have calcified external structures which
sustain their tissue and protect them from predators and environmental
perurbations. Depending on the species, this shell is formed of
aragonite, calcite or of a mix of these two minerals.
The effect of ocean acidification on shell formation depends on the
species and can even vary within strains of the same species [GAZ 07,
RIE 09]. It has also been shown that their basal metabolism could be
durably modified by the decrease of the pH projected for the end of
the century, with potentially lethal consequences in the long term
