AUSTIN, Texas -- Volunteers picked up trash from in and around Lake Travis Saturday morning for the 24th annual cleanup.

This year was different for those sorting the garbage found at the bottom of the lake by divers.

Many aluminum cans, glass bottles, and other items were covered in zebra mussels, a surprise to organizers.

"We got our first dive boat full of trash to us and opened up the bags and found that a lot of the aluminum cans that last year we were able to recycle, we are not able to recycle because they are covered in zebra mussels," said Shaun Auckland, of the Conservation Coordinator with Travis County.

None of the trash collected with the mussels can be recycled.

"It is a bit disappointing that we won't be able to recycle as much as we have been in the past," said Auckland.

The mussels will also skew some of the data collected because everything is weighed to determine how much litter was found. Volunteers typically collect 5 tons of garbage. Zebra mussels were first found in Lake Travis in the summer of 2017. The larva are microscopic and can survive in water deposits on, and in, boats, making them easy to transfer from lake to lake.

"I don't think that anybody really had anticipated just how quickly this species has taken hold here in Lake Travis. The zebra mussels have really proliferated at a huge rate. They have encrusted everything from trash itself to boats and docks,” said Geoff Hensgen, Program Director for the Colorado River Alliance. 

Organizers will likely have to make some changes to the next cleanup to account for the large amounts items that will now have to be trashed.