Final answer:
Freshwater ecosystems like lakes have the fastest turnover rates of elements due to processes like spring and fall turnovers, and thermocline formation, leading to lower mean residence times.
Step-by-step explanation:
The ecosystem with the fastest turnover rates of elements, meaning the lowest mean residence times, is typically a freshwater system such as lakes. The turnover rate is influenced by processes like the spring and fall turnover in freshwater lakes, which are seasonal events that help in the recycling of nutrients and oxygen from the bottom to the top of the water body. This is due to the formation of a thermocline, a layer of water with a different temperature compared to the layers above and below it. Marine ecosystems, on the other hand, have much slower cycles, with substances like phosphate having an oceanic residence time between 20,000 and 100,000 years.
In the context of water cycling, ecosystems demonstrate a diverse range of residence times based on their properties and the elements they cycle. Freshwater ecosystems, though less common, have shorter cycles and thus faster turnover rates due to their smaller size and the influence of air temperature and wind changes.