multiple bankroll question

[Popeye]

i have a strange hypothetical bankroll question:

lets say i have 1000$ on party poker and 1000$ on pokerstars.
Now when i sit at a table of one site, must i consider my bakroll to be 1000$ or 2000$?
so can i sit at a table for which bankroll managment rules say i need 2000$?n or only one that is low enough for 1000$?