When a worthy member of the church goes to the temple for the first time to do temple work - they participate in temple ordinances for themselves. These ordinances entail making covenants with our Heavenly Father. In return Heavenly Father covenants certain blessings with us. That is what is meant by 'blessings'. 
 
If a member of the church is excommunicated for very serious transgression (apostacy, very serious moral transgressions, etc.) then the blessings promised them in the temple are revoked/lost. 
 
Assuming the excommunicated member goes through very significant and sincere repentance they can then be re-baptized and also have their 'blessings' from the temple restored to them. 
 
Let me say that excommunication is a very significant penalty and is rarely used and only on the most serious transgressions. 
 
More information about temples can be found here: http://www.lds.org/temples/purpose/0,11298,1897-1,00.html