Geoscience Reference
In-Depth Information
phytoplankton productivity, and act as important
source regions of a range of climatically active halo-
carbons (Class and Ballschmiter 1988; Carpenter
and Liss 2000 ; Quack and Wallace 2003 ; Quack
et al.
2004 , 2007 ; Chuck
et al.
2005 ). Therefore, future
research efforts should be focused on such regions,
and involve: (1) long-term
in situ
monitoring strate-
gies to detect changes and make distinctions
between natural variability and anthropogenic
impacts and (2) bioassay experimental work, such
as on-deck incubations of water from a range of oce-
anic locations, to assess the response of complex
ecosystems and populations to elevated
p
CO
2
.
on the bacterial strains that may be involved. Such
approaches could be applied to ocean acidii cation
experiments, in mesocosms or smaller-scale bio-
assay incubations, to assess the impacts of the per-
turbation on the processes controlling the net
concentrations of trace gases in seawater.
11.4.6 Modelling studies
The ability to scale up from relatively small-scale
perturbation experiments and i eld observations to
regional and global scales using model simulations
is critical to ocean acidii cation research, enabling
researchers to assess the temporal and spatial
changes that may occur over the coming decades
(see Chapter 12). As DMS and organohalogens are
considered to exert a considerable inl uence on cli-
matic processes, the inclusion of the effects of ocean
acidii cation on these compounds in global ocean-
atmosphere modelling studies is vital to furthering
our understanding of how the entire earth system
may respond to future climate change and ocean
acidii cation.
11.4.5
Furthering a mechanistic understanding
A response of net iodocarbon and DMS produc-
tion to ocean acidii cation has been observed dur-
ing the work reviewed here. Although there is
some understanding of the processes involved for
DMS, information is lacking on the biological
mechanisms that result in net production of orga-
nohalogens and on their cycling in seawater. The
photochemistry (Moore and Zai riou 1994 ; Richter
and Wallace 2004 ; Jones and Carpenter 2005 ;
Martino
et al.
2005 ), nucleophilic substitution, and
hydrolysis of organohalogens (Elliott and Rowland
1993 ; Jeffers and Wolfe 1996 ) have been investi-
gated. In addition, the use of stable isotope tracer
techniques (e.g. production of H
14
CO
3
from
14
CHBr
3
) has provided new insight on the biologi-
cal loss rates of brominated methanes in both
freshwater and seawater, and bacteria are greatly
involved in these loss processes (Goodwin
et al.
1997 ; King and Saltzman 1997 ; Goodwin
et al.
1998 ; Tokarczyk
et al.
2001 ). Furthermore, bacteria
are probably involved in the cycling of iodocar-
bons in seawater (Amachi
et al.
2001 ). As the iodo-
carbons and DMS/P display a strong response to
ocean acidii cation ( Avgoustidi 2007 ; Hopkins
et al
. 2010), it is important to further our under-
standing of the processes controlling the net con-
centrations of these gases in seawater.
14
C- or
13
C-labelled compounds may be employed
to derive loss and production rates of trace gases in
seawater, focusing both on whole plankton commu-
nities and on the bacterial fraction, and employing
molecular techniques to gain detailed information
11.5 Acknowledgements
We thank Jean-Pierre Gattuso, Lina Hansson, Marion
Gehlen, and Laurent Bopp for reviewing this chapter.
Their helpful comments greatly improved the manu-
script. We acknowledge i nancial support from the
Natural Environment Research Council (NERC)
NER/S/A/2005/13686, the Leverhulme Trust F/00
204/AC, and Oceans 2025 (PML's NERC-funded core
program). This work is a contribution to the 'European
Project on Ocean Acidii cation' (EPOCA) which
received funding from the European Community's
Seventh Framework Programme (FP7/2007-2013)
under grant agreement no 211384.
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