Thanks, it is good to know about digestion.
The turtle is in a heated tank indoor (exept when it hibernates) and has a lid on it, so the temperature of the air above the water is as high as in the water. But I did have a problem once a few years ago: there was not enough ventilation under the lid, and the turtle got a cold. I opened the lid in both ends of the tank and thereby increased ventilation, and the turtle got back to good health during the next couple of days. Good air flow and high air temps are VERY important!