Geoscience Reference
In-Depth Information
copepod eggs [CAR 07]. Significant effects on the larval development
of copepods [CAR 07, RIE 08] and cirripedes [NIE 13] have
nevertheless been reported.
5.4.1.1.4. Viruses and bacteria
Only a few studies have investigated the effects of ocean
acidification on viral and microbial processes and diversity. These
microorganisms play a major role in biogeochemical cycles through
their capacity to remineralize particulate and dissolved organic matter
and to regenerate nutrients used by primary producers [AZA 83]. In
the framework of mesocosm experiments, changes in the bacterial
community have been observed in free bacteria, but not in bacteria
attached to particles [ALL 08]. These changes in bacterial diversity
had no impact on total bacterial production. Modifications of bacterial
production have also been observed in another mesocosm experiment
[GRO 06], together with positive effects on the activity of some
enzymes. Several subsequent studies have since highlighted the varied
effects of elevated pCO
2
on bacterial enzymatic activity [PIO 10]. For
more details on these aspects, we advise readers to consult the meta-
analysis of Liu
et al.
[LIU 10] and the summary chapter of Weinbauer
et al.
[WEI 11].
5.4.1.1.5. Fish
It has long been considered that the acidification of the ocean does
not have any significant impact on fish. Historically, studies of
hypercapnia (elevated pCO
2
level) in fish have focused on acid-base
balance and have generally been carried out at pCO
2
levels of 10,000-
50,000 μatm [ISH 04]. However, several recent studies have shown
that the ocean acidification can affect fish at CO
2
levels representative
of those expected in the coming decades. Among noteworthy
observations is the influence of ocean acidification on the formation of
otoliths of the white bass [CHE 09], the survival and growth of the
North American silverside [BAU 11] and on the respiratory
physiology and acid-base balance of the gulf toadfish [ESB 12].
Elevated CO
2
also seem
to cause irreparable damage to the tissues of
cod larvae [FRO 12]. Other much less expected effects have been
reported for reef fish. Acidification affects the olfactory ability of
certain species, disrupting habitat selection [MUN 09], hearing
