The deeper colored graining seems to be small branches and twigs frozen in the ice just below the surface? The lighter graining seems to be thin stress fractures in the ice. This is on a small still backwater channel of the main lake sheltered from the wind. Strangely, over to the far right center are two shiny objects which may be coins people have thrown on the ice?
Included is a second picture to give some perspective to the location. Similar ice is just starting to show in the foreground.