BROOKLYN - The MTA will close nine northbound N train stations for renovations, complicating commutes for straphangers in South Brooklyn.

Signs at the stations say the work on the Sea Beach line begins on Jan. 18., but many riders say they had no idea this was coming. It's expected to take about a year.

The affected stations are at Eighth Avenue, Fort Hamilton Parkway, New Utrecht Avenue, 18th Avenue, 20th Avenue, Bay Parkway, Kings Highway, Avenue U and 86th Street.

Riders will have to go southbound to Stillwell Avenue and then take an express N into Manhattan.