Geoscience Reference
In-Depth Information
is the result of the increase in the number of national
and international projects on ocean acidii cation
and the consequent increase of the rate of publica-
tion (see Chapter 1). It now seems that the overall
magnitude of the workforce is no longer a major
impediment for ocean acidii cation research. Other
difi culties, such as technological and conceptual
limitations, hamper progress towards a better
understanding of the consequences of ocean acidii -
cation. However, some key areas such as work at
the community level as well as social and economic
science are still limited by the number of scientists
involved.
−
inappropriate normalization of measured data
(e.g. normalizing per cell and per unit biomass
may yield very different interpretations if cell
size differs between treatments).
These and other possible pitfalls in ocean acidii ca-
tion research are addressed and recommendations
for proper experimentation provided in the
Guide to
best practices for ocean acidii cation research and data
reporting
(Riebesell
et al.
2010a). It is therefore hoped
that future experiments will strictly follow these
guidelines, hence helping to avoid confusion in the
literature generated by inconsistent methods and
data reporting.
15.4.2
Inappropriate or inconsistent methods
15.4.3
Duration of experiments
As more and more results on the sensitivity of
organisms and communities to ocean acidifica-
tion become available, the breadth and depth of
our understanding of causes and consequences
grows. At the same time, the evolving picture
becomes blurred by conflicting results. While
part of this may simply reflect species-specific
differences or the plasticity of organisms in
responding to environmental stressors, part of
the discrepancy may result from inappropriate
methodology, poorly constrained experimental
protocols, or misinterpretation of the data.
Inconsistencies of this sort may originate from
shortcomings such as:
The current anthropogenic ocean acidii cation is a
very fast process compared with previous episodes
in the geological past (Section 15.2.1.3; see also
Chapter 2) but still long compared with the genera-
tion time of most marine organisms. Adaptation,
i.e. adjustment to environmental change by genetic
change, is much more likely in microbes than in
multicellular marine organisms because they repro-
duce quickly relative to the timescale of global
change and have large populations (Section 15.2.2.5).
Their short generation time of a few days allows for
thousands of generations by 2100, hence increasing
the accumulation of mutations and, at least for
prokaryotes, more efi cient lateral gene transfer.
Perturbation experiments have been the method of
choice for investigating the effects of ocean acidii -
cation. They were conducted over periods of time
(hours to weeks) that may have been long enough
to reach a steady-state physiological response but
too short to reach a 'steady-state' evolutionary
response. There is a strong need to carry out longer
experiments, encompassing hundreds or thousands
of microbial generations. Such experiments have
been performed in a green microalga found in soils
and freshwater (Collins and Bell 2004, 2006), pro-
viding interesting insight for ocean acidii cation
research. First, lines of this alga either increased
photosynthesis without increased growth or both
their growth and photosynthesis were insensitive to
elevated CO
2
. Specimens found in the vicinity of
natural CO
2
springs exhibited a similar phenotype,
− insufi cient control and incomplete description
of seawater carbonate chemistry,
− interference through confounding factors, such
as temperature, nutrient and oxygen concentra-
tions, irradiance and diurnal cycles,
− lack of acclimation of the test organisms to exper-
imental conditions, causing stress- rather than
treatment-related responses,
− pseudoreplication, i.e. the lack of independent,
interspersed replicates at the treatment level,
− use of isolates kept in culture over years and dec-
ades which may have undergone phenotypic or
genetic change unrelated to ocean acidii cation,
− reporting and interpreting observed responses in
relation to mean values, e.g. of pH and
p
CO
2
,
when in fact large variations in carbonate chemis-
try occurred during the experiment,
