BIOACID Programme - Natural Environment Research Council

BIOACID: Biological Impacts of Ocean Acidification
on calcite forming phytoplankton (Gehlen et al., 2007) and aragonite forming zooplankton
(Gangstø et al., 2008). Furthermore, she has worked on sensitivity studies estimating the
relevance of changes in the vertical flux of particulate organic and inorganic carbon (POC, PIC)
on the uptake and storage of CO2 by the ocean, which have demonstrated the potential for
considerable and persistent effects on the atmospheric CO2 concentration (Schneider et al. 2004;
Schneider et al., 2008b).
iv. Detailed Description of the Project Work Plan
In a first step (six months) an extensive review of what is currently known about the processes
contributing to the production and decomposition of DOC and TEP will be summarized.
Therefore, next to current literature the experience of the collaborators within Themes1 and 3 and
their hypotheses for the new experimental setups will be explored, in particular the dependence
of POC/DOC/TEP production and decay on pH and/or pCO2 (Schulz, 3.1.1; Engel, 1.2.1;
Grossart, 1.2.4; Müller, 1.1.3; Nausch, 1.2.3, and Voß, 1.2.2, temperature (Müller, 1.1.3, Voß,
1.2.2), light and nutrients (Hippler, 1.1.2; Nausch, 1.2.3, Voß, 1.2.2) as well as the role of DOC
and TEP in the formation and fate of marine aggregates (Engel, 1.2.1, Thomsen, 1.2.5; Riebesell,
3.2.1. Examples from paleo analogues will be considered in collaboration with two sub projects
from Theme 3 (Mutterlose, 3.5.2; Meier, 3.5.3). In a second step (one year) the current
implementation of DOC cycling in the marine biogeochemical model PISCES (Aumont and
Bopp, 2006) will be revised. Therefore, together with participants from Themes 1 (see above), 3
(Hoppema, 3.4.3) and 5 (Pätsch, 5.1; Oschlies, 5.2) and with colleagues at LSCE (France) new
parameterizations for DOC cycling will be developed and implemented into PISCES. If
available, these parameterizations should already include new experimental results obtained in
Themes 1 and 3. The major points to be addressed here will be the effects of changes in the
environmental conditions (pCO2, pH, temperature, light, nutrients) on (1) species specific DOC
exudation rates of the (four) plankton functional types represented by the model, (2) DOC
mineralization, and (3) the influence of DOC (TEP) on particle aggregation. For the latter a
higher (lower) abundance of DOC and thus TEP will automatically increase (decrease) the
frequency of collisions between DOC and particles and thereby favor (inhibit) aggregate
formation, however, an increase in the stickiness of organic material with lower pH as observed
by (Engel et al., 2004) is so far not considered by the model. In the following phase (1 year) the
complex interplay of physical and biological responses to anthropogenic CO2 perturbations on
the marine carbon cycle and potential climate feedbacks will be addressed by the application of a
state-of-the-art coupled climate carbon cycle model (KCM - Kiel Climate Model, PISCES). By
driving the biogeochemical model with pre-determined ocean circulation fields for either
constant or changing climate conditions the effects of ocean acidification and global warming
will be assessed separately and in combination. The final step (six months) will be the synthesis
of new DOC and TEP related findings from Theme 1 that will also be relevant for the
synthesizing projects in Theme 5 (Oschlies, 5.2; Quaas, 5.3).
Work Schedule
1.3 First Year Second Year Third Year
review sensitivity of DOC and TEP to
changes in environmental conditions
I II III IV I II III IV I II III IV
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