In this case, only the distinction between articles le (pronounced /lə/) and les (pronounced /le/ or /lɛ/) marks the difference.

In most cases, the added s does not change the pronunciation, but sometimes a liaison between an adjective and the noun may change:

un grand espace /œ̃.ɡʁɑ̃.(t‿)ɛs.pas/
de grands espaces /də.gʁɑ̃.z‿ɛs.pas/

la grande ère glacière /la.ɡʁɑ̃.d‿ɛʁ.ɡla.sjɛʁ/
les grandes ères glacières /le.ɡʁɑ̃d(ə).z‿ɛʁ.ɡla.sjɛʁ/

And as always, the occasional exceptions.