Evolutionary pressures on planktonic production of atmospheric sulfur
Phytoplanktonic production of dimethylsulfide (DMS) plays an important role in climate regulation. This is an investigation of what evolutionary pressure caused phytoplankton to begin producing DMS.
Dimethylsulfide (DMS), produced by marine phytoplankton, has been proposed as the major source of cloud condensation nuclei (CCN) in the remote marine atmosphere, and as an important factor in global climate. Charlson et al suggested that climate modulation and altruism may have been significant factors in the evolution of DMS production by marine phytoplankton. These proposals have led to a re-examination of the relationship between the Earth's biota and climate. Calculations of relative evolutionary pressure in models of individual selection and group selection suggest that neither climate modulation nor altruism could have been the primary factors in the evolution of mid-ocean DMS production. Although a DMS/climate feedback loop may have a role in modulating fluctuations in the Earth's climate, the explanation for mid-ocean DMS production can be found primarily in selection based on local interactions, for example, osmoregulation, and not in evolutionary feedbacks from proposed climate modulation.