Some egg capsules may survive and repopulate your garden area. How long will salt stay in that soil.

I don't know how long the salt stays in but it must wash out little by little each time it rains.

Last year we had a shorter salt water soaking from hurricane Irene, but it rained heavily for a week or two after. Worms and slugs were not wiped out like this time but were clearly diminished.

Just get to mulching as a start. I suspect it will bounce back. Hopefully without the slugs.

OVERDUE UPDATE:

Only saw a few worms in my compost pile the next year, a few more the next.

Third year both worms and slugs back to normal. Oh, and snails too.