This is Janusz Pond a few years ago. It borders the Polesian National Park in Western #Polesia. A few ponds like Janusz were included in the park on its formation in 1990 and they look much wilder.
This is Janusz Pond today. All the water has been let out exposing the muddy bottom. The company that operated the pond did not extend its lease and the whole fish operation was shut down.
On closer look the spots turn out to be dead swan mussels (Anodonta cygnea), a species found only in very clean water.
There are no swan mussels left, only their shells remain. #IdaPsięta are very disappointed.
@szescstopni are they edible?
@RoboticistDuck They're used as animal feed, I'd have to check on use by humans. Probably not very tasty .
Those mussels are some of the largest freshwater mussels, reaching 20 cm in length. The pocket knife placed for comparison is 9 cm long.