Yup... Nightcrawlers have been decimating my carrot seedlings for a couple of years now. I have ruled out other things such as slugs, damping off, earwigs etc. I mulch my garden pretty heavily, but the carrot beds were intentionally left clean to avoid competition for the emerging seedlings.. The poor worms were just hungry. They came up, looked around - nothing to eat except carrot seedlings - oh well, better Garth's carrots than nothing... chomp - chomp - replant - chomp - chomp... So I started mulching the bed with grass clippings and more seedlings survived. Ready to do war again this year. Perhaps I will string bright lights over the carrot bed. I simply have too many worms in my ultra rich organic soil. They know a good thing when they find it. I have photos of the stockpiles of debris over their holes. Amazing critters.

I have a solution for you! My problem was similar to yours. I have a small patio for a large lawn swing underneath 2 large Norway maple trees. It was left undisturbed for 25 years and by now the cracks between the 2 ft. square pavers were about 4 inches high with dirt, plus grass and weeds growing rambunctiously thereon. I cleaned off 2 squares. On one, I dug out an extra 3/4 inch of ground and filled it with used cat litter. (clumping, therefore sodium bentonite kind) On both, I planted moss which I had scraped out of my grass. The very next day the square with just the moss was completely uplifted with worm castings! For the first time I looked closely at the soil and realized it was all worm castings. For 5 days I watched and although the moss turned brown and seemed to die on the cat litter, not a single worm casting appeared! I've been experimenting with used cat litter and used it here to try to prevent weeds from sprouting in the cracks. Eureka! Preventing the worm castings was MUCH better. So now I've re-done that entire patio with 3/4 inch of cat litter in the cracks. I really like the look of moss there so I went to the woods and brought home 3 kinds of moss. Some have a thin layer of roots and soil. Some have a thin layer of roots and bark; so we'll see if any kind survives. The original moss I tried had no roots or soil and it survived on the bare ground but got heaved out with the worm castings.

On other forums there is some discussion about the use of the liquid "aerators" called Aerify and Nitron. Generally they seem to work when used frequently. One of those is a soap based product and the other seems to be based on yucca extract. Both of those materials are surfactants. If you want to try that out without paying a huge premium for soap, I would try some generic baby shampoo from wherever. Put it full strength into your hose end sprayer (or mix it with beer like Jerry Baker ;0 ). Adjust the sprayer so that you see just see foam coming out. Spray monthly for 3 months and then skip to every other month. The idea of the surfactant is to break the surface tension of the water and allow it to penetrate deeper. The screwdriver does somewhat the same thing by opening up holes for the water to penetrate the first 3 inches without resistance. Your light yellow grass with the seeds sounds like poa annua. You'll have puhlenty of that next year. I think preemergents were designed for poa annua. Deep infrequent watering won't affect the grubs but it will positively affect the beneficial fungi. You want fungi. The soapy water should help, there, too. The best organic control for grubs in the south is beneficial nematodes. In the north milky spore seems to work better. Both have their idiosyncrasies. Beneficial nematodes need very wet soil to move around. Apply during a heavy rainstorm. Like now would be good in Tennessee. Milky spore needs to have a big presence in the soil. Seems that repeated apps every 6 months for 3 years is needed.

Pine bark mulch is OK for earthworms, in that it won't kill them. It will actually provide some beneficial cover and insulation from the winter elements. As it breaks down in a couple of years, the earthworms will like it much better. If your goal is to benefit earthworms, they would be even more appreciative of a softer "forest floor" environment like shredded leaves, hay, or pine needles - especially with some used coffee grounds or kitchen scraps mixed in. But if your goal is to get rid of pine bark mulch without harming the worm population, then you can sleep soundly knowing that the worms will be happy underneath the bark.