It is very disturbing, Rachel.
Monofilament line (which is what this appears to be), such as found in recreational fishing as well as commercial fishing products, has been a horrific hazard to sea life and wetland wildlife for decades. Once an animal becomes entangled in, or ingests, this stuff it's nearly always an agonizing, slow death sentence.
The chemical companies that make this stuff have made sympathetic noises for a generation, promising to develop products that would be less collaterally hazardous to wildlife. But it's mostly been air movement.
If you're reading this, and you're also an angler or regularly use mono line, please, please be careful with his stuff.