6.6 Marine Microorganisms and Their Influence on Global Climate and Global Nutrient Recycling 143
Fig. 6.13 Breakdown of DMSP in water. Microbial transfor-
mations involved in the turnover of DMSP and DMS in marine
surface waters. Abbreviations: DMSP dimethylsulfoniopropi-
onate, DMS dimethyl sulfide, DMSO dimethylsulfoxide,
MMPA methylmercaptopropionate, M PA mercaptopropionate.
DMS is the most important biologically produced sulfur com-
pound in the marine atmosphere (From Welsh 2000. With
permission)Fig. 6.14 Schematic representation of the processes involved
in DMS oxidation, climate regulation, and coupling of the oce-
anic and terrestrial sulfur cycles. The oxidation of DMS by
hydroxyl and nitrate radicals results in the formation of sulfate
aerosols, which on advection into water saturated air cause cloud
formation. Both increased cloud formation and dry sulfate aero-
sols increase planetary albedo resulting in a relative cooling
effect. Dry deposition of sulfate aerosols and precipitation of
sulfate enriched rainwater over the continents couples the marine
and terrestrial sulfur cycles. Rainfall over the oceans may pro-
vide a feedback between DMS production by micro-algae and
their productivity due to increased inputs of dissolved nutrients
or by providing a dilute inoculum of micro-algal cells trans-
ported within the clouds. (From Welsh 2000. With permission)