How does rising atmospheric CO2 affect marine organisms?

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Dimethyl Sulfide: It's Role in Stabilizing Earth's Climate
Ayers, G.P. and Gillett, R.W.  2000.  DMS and its oxidation products in the remote marine atmosphere: implications for climate and atmospheric chemistry.  Journal of Sea Research 43: 275-286.

Several years ago, Charlson et al. (1987) discussed the plausibility of a feedback process that links dimethyl sulfide (DMS) with climate.  The basic tenant of their hypothesis was that the global radiation balance is significantly influenced by the albedo of marine stratus clouds.  The albedo of these clouds, in turn, is known to be a function of cloud droplet concentration, which is dependent upon the availability of cloud condensation nuclei on which the droplets form.  In completing the feedback loop, Charlson et al. further noted that the cloud condensation nuclei concentration often depends on the flux of DMS from the ocean.

What was done
Acknowledging that the roles played by DMS oxidation products within the contexts mentioned above are indeed "diverse and complex," and in many instances "not well understood," the authors summarize empirical evidence in support of Charlson et al.'s hypothesis from data collected at Cape Grim, Tasmania since 1988, as well as from what has been reported in prior peer-reviewed papers on the subject.

What was learned
According to the authors, "major links in the feedback chain proposed by Charlson et al. (1987) have a sound physical basis," and there is "compelling observational evidence to suggest that DMS and its atmospheric products participate significantly in processes of climate regulation and reactive atmospheric chemistry in the remote marine boundary layer of the Southern Hemisphere."

What it means
The empirical evidence analyzed by the authors highlights an important negative feedback process that acts in opposition to model-predicted CO2-induced global warming.  At present, these processes are not fully incorporated or quantified in the best of today's climate models.  When they are, you can be sure that the amount of warming the models predict will be significantly lowered.  And when similar terrestrial processes driven by an increase in atmospheric CO2 concentration are considered (Idso, 1990), model predictions of global warming may be erased altogether.

Charlson, R.J., Lovelock, J.E., Andrea, M.O. and Warren, S.G.  1987.  Oceanic phytoplankton, atmospheric sulfur, cloud albedo and climate.  Nature 326: 655-661.

Idso, S.B.  1990.  A role for soil microbes in moderating the carbon dioxide greenhouse effect?  Soil Science 149: 179-180.