Effects of ultraviolet radiation on Production and degradation of dissolved organic matter in the sea

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Natural and artificial seawater were evaluated to study on Chromophotic Dissolved Organic Matter (CDOM) as an index of Dissolved Organic Matter (DOM). Filter types were also compared to obtain particle-free filtered seawater. Cultural phytoplankton grew better in the filtered natural seawater. Anodisc filters eliminated most particles from seawater. Several phytoplankton group were examined and diatoms grew as well as bacteria and CDOM increased even in the filtered seawater. Under a dark condition, both diatoms and bacteria did not grow. But not bacteria grew in the Anodisc filter seawater and consequently no production of CDOM occurred. Those series of experiment may suggest that phytoplankton produce CDOM and bacteria utilize those CDOM. Under Ultraviolet Radiation (UVR) in addition to PAR, the growth rate of diatoms was depressed compared to PAR only. However the amounts of CDOM per cell were higher with UVR than one without UVR. In summary CDOM can be effectively employed to study dynamics of DOM, the present incubation methods can be applied to evaluate the ecological role of DOM in the ocean.