What would you have done : plastic in mulch

I share a garden with someone who wanted to be all permaculture and collected a bunch of seagrass to use as mulch. Sounds great, right? Except instead of using it straight away, they left it sitting outside in plastic bags for ages. Now the bags have disintegrated, and there are tiny bits of plastic EVERYWHERE

I finally had enough and tried to clean it up—got as much of the plastic out as I could and spread the seagrass on the garden, but it’s still pretty contaminated. So frustrating when something meant to be eco-friendly turns into a mess like this.

Anyone else dealt with something like this?How do you even begin to clean up tiny plastic bits once they’re in the soil?