I use coinbase as my BTC wallet.
Now there is considerable fee for sending BTC.
Poloniex is providing me a BTC deposit address.

Please help me in the following doubts.
(1) I have a few BTC investment/mining sites.
     Can I link my Poloniex BTC deposit address to that sites so that my withdrawals from that sites are directly deposited to my Poloniex account?

(2) What is the minimum amount for BTC deposit in Poloniex?
    That is, can  I send 0.0009 BTC, 0.001 BTC etc to my Poloniex BTC deposit address to get credited in my Poloniex account?