Marine microplastic pollution is very tiny (< 1/4") pieces of plastic that wash into the oceans. Some of these pieces are almost microscopic. Many are tiny fibers that wash out of our clothes in the laundry.
Marine microplastic pollution is harmful because it gets into the food chain. Tiny plankton cling to the plastic fibers. These are eaten by baby fish which are then the base of a much larger food chain, culminating in fish and seafood eaten by humans.
The microfibers are pulled out of our synthetic clothing in the washing machine. This gradually degrades the clothing as well as polluting the water.
A European firm has developed a tightly-woven polyester monofilament bag to protect the clothes and capture the microfibers. This is a nice idea but I can’t see spending $35 for a garment washing bag. There are several alternative washing bags that are cheaper. I’d have to look at them to see how tightly woven they are (to filter detached fibers).
To preserve your clothes and help protect the oceans
Buy natural fiber (biodegradable) fabrics instead of synthetic.
Wash on “gentle” instead of “regular” to reduce abrasion in the wash.
Put the most likely to “shed” (e.g. fleece) in a garment washing bag.
I’m not sure how this helps exactly. Maybe the lint collected in your dryer somehow ends up in the ocean?
I’ve also hear that carpet fibers were one of the most detected fibers in the ocean. Seemed like a ridiculous claim. A few year ago I had some carpet replaced and the installers did a very careful and nice job.
(By coincidence when the company showed up to do the install the lead installer happened to be someone I knew from my racquetball gym for 10+ years). But years later I still find a few ~1/2" to 1" in my front garden every so often. No doubt that some blew to the gutter and down the storm drains.