A rise in temperature increases the rate of cellular respiration. This is due in part to an increase in amount of oxygen needed to carry out processes in the cell.
The affect of temperature on oxygen affects not only the need for oxygen but the amount of oxygen available to an organism. Organisms that live in water that increases in temperature will have less oxygen available in the water to pull into their cells. In cellular respiration, the oxygen is used to help process and create energy and heat for the body. Most organisms release the excess heat in some way, but if the amount of oxygen is low, then the amount of heat will be lower as well, making it harder for an organism to maintain its ideal body temperature.