Williams confirmed on Wednesday that Bottas will join Pastor Maldonado for next season.
"Since the beginning of my program with Williams I accepted that I had to share the car with Valtteri Bottas in 15 Fridays as a part of his preparation for a likely début in 2013", Bruno explained.
Senna raced for HRT in 2010 before moving to Lotus for the last eight rounds of the 2011 season. Senna moved to Williams in January, finishing in 16th in the drivers standings with 31 points, the first time he contested a full season.
"It has been extremely satisfying to be the teams most regular point scorer and for me to demonstrate my pace in all 20 races. I have learned a lot and improved considerably through the season. I have had a relatively short career so far and feel as though I have come a long way in just a few years".
Senna showed a special gratitude to Sir Frank Williams, a name strongly linked to Formula 1 history.
"I would like to thank the whole team and particularly Frank for giving me the chance of completing my first full season in F1. It has been extremely rewarding to develop the Williams FW34 into a consistently competitive race car and cracking the challenge of the Pirelli tyres has been just one of the satisfying points."
"I had some notable achievements this year, such as the fastest lap in the Belgian GP, my favourite track, scoring points on a regular basis and making up many many places through the races. Regularly racing in the top ten has certainly been a step forward in my still relatively short career and has allowed me to further sharpen up my race craft. Working with a competitive and supportive engineering team like Williams has left me well prepared for the next step in my career".
Senna will announce his 2013 plans soon.