Human activities have an effect both on the local and global environment and disturbances (changes in environmental factors) are widely believed to be one of the main factors influencing variations in species diversity. Microorganisms are found in high abundances in all environments and are important for decomposition and transformations in the carbon, nitrogen, sulfur and phosphate cycles. In aquatic environments microorganisms are also an important link between dissolved organic matter and higher trophic levels. Despite the importance of microorganisms for ecosystem functioning they have mostly been overlooked in biodiversity research. The importance of bacterioplankton community composition and diversity for community function and response to disturbances is therefore still poorly understood. I study the effect of disturbances on bacterial community composition, diversity and functionality (ability to utilize dissolved organic carbon). I’m also interested in how composition and diversity of the bacterial community affect resistance and resilience when bacterial communities are exposed to disturbances.