Water body temperature is one of the most ubiquitous variables collected in aquatic biomonitoring. Temperatures at the water surface, through the water column, and in the lowest levels of the water body (benthic zone) can all provide insight into different aspects of an aquatic ecosystem. Water temperature is directly affected by climate change and can have negative affects on many aquatic species, such as salmon. Salmon spawning is temperature dependant: there is a heat accumulation threshold which must be reached before hatching can occur. Post-hatching, salmon live in water within a critical range in temperature, with exposure to temperatures outside of this being potentially lethal. This sensitivity makes them useful indicators of changes in water temperature, hence their use in climate change studies. Similarly, Daphnia populations have been evidenced as being negatively affected by climate change, as earlier springs have caused hatching periods to de-couple from the peak window of food availability.