My extremely crappy translation. Some are pure speculation. Please, anyone, correct this if you can. 
"Apparently everyone has read the news, but I hereby announce that our leader Yaguchi Mari has resigned from Morning Musume and would continue solo."
And the arena became dead silent.
"And thus Yaguchi-san is not showing up in today's concert. Much apology to Yaguchi-san's fans. (Members bowed) Although Yaguchi-san has not explained to anyone the reason why she resigned, we are very understandable of her situation since we have always been together. We understand some fans don't agree with her decision, but we think that this is really her clean-cut way of doing things. Please sympathize with Yaguchi-san's feelings."
The audience clapped their hands.
"(her tone brightened up a little) Though Yaguttsuan left us suddenly, please continue to support us and make today's concert a blast (applause). Of course this is also Yaguchi-san's wish (applause). We are going to do our best (with Yaguchi-san's energy?!). With that said, Morning Musume's concert shall start."