Lake temperatures will increase but dissolved oxygen in the water will decrease. Water vapour is a potent greenhouse gas, so global temperatures will increase, including lake temperature. Additionally, increased water vapour in the air will decrease the amount that can evaporate from the lake and further reduce the amount that it can cool, in which makes the water warmer still. Water temperature increases mean decreased the solubility of gases (above 4 degrees C), so dissolved oxygen would cease to decrease on a ppm basis. I hope this answer has helped you.