How does rising atmospheric CO2 affect marine organisms?

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Climatic Effects on Oceanic DMS Producers
Reference
Wong, C.-S., Wong, S.-K. E., Pena, A. and Levasseur, M. 2006. Climatic effect on DMS producers in the NE sub-Arctic Pacific: ENSO on the upper ocean. Tellus 58B: 319-326.

Background
Dimethylsulfide (DMS), which is derived from its algal precursor dimethylsulphoniopropionate (DSMP), is a climatically-important trace gas that has its origin in the activity of certain types of marine phytoplankton and is believed to play a major role in keeping earth's temperature within bounds that are conducive to the continual existence of life. Very briefly, and rather simplistically, in response to an initial warming (caused by an increase in the air's CO2 content, for example), the climate-stabilizing mechanism begins with a warming-induced increase in the productivity of certain marine phytoplankton, which leads to a greater production of oceanic DMS and its release to the atmosphere, which boosts the number of gas-to-particle conversions, increasing the atmosphere's population of cloud condensation nuclei and, ultimately, the albedos of marine stratus and altostratus clouds via a narrowing of the cloud droplet spectrum and a decrease in the mean radius of the cloud droplets, both of which phenomena tend to counteract the initial impetus for warming.

What was done
From 1996 to 2001 the authors recorded DMS concentrations and physical oceanographic data at ocean stations P26 (50N, 145W) and P20 (4934'N, 13840'W) in the Gulf of Alaska in the Northeast Pacific Ocean, after which they analyzed the data in a number of different ways.

What was learned
Wong et al.'s work confirmed that as the sea surface temperature of a region rises, "the stratification of the upper water column intensifies and oceanic upwelling weakens," such that "in the nutrient-rich waters of the sub-Arctic Pacific, higher stratification and shallower mixed layer favor the growth of small-sized phytoplankton such as flagellates, dinoflagellates and coccolithophorids." And noting that "most prolific DMSP producers are members of these phytoplankton groups," they say that, "consequently, the local ecosystem is shifted towards one with structure and function adapted to [increasing] production of DMSP and DMS."

What it means
Quoting the four researchers, "globally, a larger part of the warming oceans may have highly stratified water for a longer part of the year," and they say that "these conditions could enhance the shift in the marine ecosystem described herein, and might induce more rapid turnover of DMSP and higher production of DMS," such that "in a warming global climate, we might anticipate an increasing emission of biogenic DMS from the ocean surface," which, of course, is a phenomenon that would tend to counteract whatever impetus for warming was causing sea surface temperatures to rise, thereby slowing or negating their upward progression.

Reviewed 7 February 2007