Turns has captained Premier League club Brighton's under-21 side after coming through their academy and has made two first-team appearances in the Carabao Cup. The 22-year-old spent part of the last two seasons on loan at League One side Leyton Orient and also had a spell with Crewe Alexandra.
Manager Gary Caldwell spoke on the move and believes he can develop at the club after a limited amount of games with the Seagulls.
“Ed is a young player with huge potential that has experience of League One, and has played a lot of football for his age. He has won League Two.
“We believe he is the type of player we want to be signing. We can develop him to help the team, and as a permanent signing, he is here on our terms and we don’t have the risk of losing loan players. He is a ball-playing center-back who is aggressive out of possession and adds to an area of the team that is seriously depleted.”