On polo there are stored still 9 mio steem, but on bittrex 35 mio.
So polo isn't so important for steem, but nevertheless this is not so good news.
On the other hand, the amount of SP is rising since several days, up to 206 mio now.
Over all, I'm not very worried about steem.
In the next BTC bull run steem will also rise measured in USD.