Increases in concentrations of greenhouse gases projected for the 21st century are expected to lead to increased mean global air and ocean temperatures. The assessment considered the impacts of several key drivers of climate change: sea level change; alterations in precipitation patterns and subsequent delivery of freshwater, nutrients, and sediment; increased ocean temperature; alterations in circulation patterns; changes in frequency and intensity of coastal storms; and increased levels of atmospheric CO2. Although these potential impacts of climate change and variability will vary from system to system, it is important to recognize that they will be superimposed upon, and in many cases intensify, other ecosystem stresses (pollution, harvesting, habitat destruction, invasive species, land and resource use, extreme natural events), which may lead to more significant consequences. Microbes are the organisms which change first among other organisms in response to the changing environment. Hence, the change of microbial community and the observation of DNA damage due to acidification of seawater can be useful indices to understand the effect of climate change. Here, three basic aspects are reviewed : i) the effect of lowering pH and enhanced temperature due to ocean acidification and ocean warming on the DNA backbone in the marine microbial cells ; ii) CO2 increase may induce the bacterial cells to uptake and help in DMS and seeds cloud formation ; and iii) index for the effect of climate change in ocean due to DNA damage.