Geoscience Reference
In-Depth Information
Table 15.1 Summary of the knowns, unknowns, and challenges related to ocean acidii cation. The recommendations of Mastrandrea et al. ( 2010 ) were
used for the levels of evidence ('limited', 'medium', or 'robust') and coni dence ('very low', 'low', 'medium', 'high', and 'very high'). For statements related to
projected impacts of anthropogenic ocean acidii cation, ranges of p CO 2 , pH, CaCO 3 saturation state, etc. projected for 2100 under business-as-usual CO 2
emissions (e.g. generating atmospheric CO 2 concentrations of 793 ppmv in 2100) are considered. Question marks indicate that the effect is unknown. The
chapters in which detailed information can be found are indicated.
Statement
Level of
evidence
Level of
coni dence
Challenges
Chapter(s)
Chemical aspects
Ocean acidii cation occurred
in the past
Robust
Very high
Better constrain palaeoreconstructions of the
carbonate system
2, 3
Ocean acidii cation is in
progress
Robust
Very high
Better monitoring of key areas (e.g. coastal sites,
coral reefs, polar regions, and the deep sea)
1, 3
Ocean acidii cation will continue
at a rate never encountered
in the past 55 Myr
Robust
Very high
Find two independent carbonate chemistry proxies
to reconstruct the ocean carbonate chemistry
with a high degree of coni dence
2, 3
Future ocean acidii cation depends on
emission pathways
Robust
Very high
Improve the representation of physical regimes at
the regional scale to derive regional estimates
3, 14
The legacy of historical fossil fuel
emissions on ocean acidii cation will
be felt for centuries
Robust
Very high
Improve the representation of physical regimes at
the regional scale to derive regional estimates
14
Biological and biogeochemical responses
Ocean acidii cation will adversely affect
calcii cation
Medium
High
Determine the mechanisms explaining that a few
calcii ers are not affected or stimulated. Gain
i eld evidence in addition to that available from
CO 2 vents. Identify approaches to improve
attribution on i eld observations
4, 6, 7
Ocean acidii cation will stimulate
primary production
Medium
High
More work needed at the community level and
under i eld conditions to better assess the global
magnitude of the response
6, 7
Ocean acidii cation will stimulate
nitrogen i xation
Medium
Medium
Investigate more species to test whether it is a
widespread response. Determine the interaction
with other variables in order to better assess the
global magnitude and biogeochemical
consequences
6
Some species or strains are
tolerant
Robust
Very high
Gain a better understanding of the molecular and
biochemical mechanisms underlying processes
such as calcii cation
6, 7
Some taxonomic groups will be
able to adapt
Limited
?
Identify approaches and tools to estimate the
adaptation potential
4, 5, 6, 7, 8
Ocean acidii cation will change
the composition of
communities
Robust
High
Collect better information on non-calcii ers in the
palaeorecord and determine the magnitude of
the change in present key ecosystems
4, 5, 6, 7,
9, 10
Ocean acidii cation will impact
food webs and higher trophic levels
Limited
?
Determine how species that may disappear will be
replaced and whether the nutritional value of
the replacement species may change
6, 7
Ocean acidii cation will have
biogeochemical consequences
at the global scale
Medium
Medium
A better understanding of key processes as a
function of carbonate system variables is critically
needed to improve model parameterization
11, 12
(continued )
 
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