Cellular contents of DMSP and DMSO in diverse marine phytoplankton

Abstract

Dimethylsulphide(DMS) is the major sulfur compound in the ocean, having a significant influence on the global climate change .DMS can go into the air and undergo oxidation to form acidic aerosols and condensation nuclei, thereby increasing the reflectivity of the cloud, which will reflect more sunlight back into outer space, decreasing the temperature of the earth. Dimethylsulphoniopropionate (DMSP) is the precursor of DMS, it can be decomposed into DMS through several biochemical processes. DMSO is the oxidization product of DMS. In the material recycling system, the content of DMSP and DMSO will be related to the DMS content in the ocean. Recently, the study of factors (light intensity and length, temperature, nutrient) affecting the DMSP production draws more attention. But few researches were reported about the DMSP production change caused by pH

furthermore, in well-fed exponential stage, pH is only the variation factor that may influence the DMSO and DMSP production. The relationship between DMSP and DMSO production also has few reports. So this study focused on the effect of pH on the particulate DMSP production change during the exponential phase, the particulate DMSP (DMSP p) and particulate DMSO (DMSO p) content in some species of phytoplankton, in order to make contribute to study of DMSP and DMSO. Several DMSO measurement methods were conducted and compared. We selected cobalt-doped NaBH4 to reduce DMSO and improved the sequential procedure to measure DMSP and DMSO. During the procedure of sampling DMSP p and DMSO p, cell is easy to break, DMSO p and DMSO p will be release to the medium. DMSP is also likely to be decomposed into DMS during this procedure. Thus, selecting a proper filtration method is vital to this study. After comparison, gravity filtration method was chosen to reduce the damage on the algae cells.5 species of phytoplankton were cultured to examine the effect of pH on the particulate DMSP production during exponential stage. It was found that during the well-fed stage, pH is a pivotal factor affecting the DMSP production in phytoplankton cells. Particulate DMSP production will be constant if the pH of the medium is well stabilized.The DMSP and DMSO production during the whole growth stage were monitored. The production decreased during the stationary phase and decline phase, it may due to the deceased biological activity.10 species of phytoplankton (including diatoms, dinoflagellates, prymnesiophytes) were cultured to measure the particulate DMSP and DMSO quota in each species. The results indicate that all the cultured phytoplankton can synthesize DMSP and DMSO in their own cells, but the capacity depends on species. In this study, a time-saving and high precision method was improved to measure DMSO. Result the relationship between particulate DMSP and DMSO from this study could have significance for our understanding of the mechanisms involved in DMSP and DMSO production.