Lakes like other biological systems age over the passage of time. Lakes age naturally over a geologic time scale and they should not exhibit age-related changes over a human’s lifetime. Lake succession is a term used to describe the process of continuous aging in a lake in terms of their physical and biological properties. Lake succession is expressed in terms of age, from young, to middle-age and finally to old-age. As the biological properties of a lake age, they reach different biological growth states referred to as trophic states. The term trophic status refers to a level of primary productivity or growth in the algae and plant community of a lake. Young lakes have a low primary productivity whereas old-age lakes have high levels of primary productivity. The term eutrophication refers to the change in a lake from having lower level of primary productivity to a higher level of primary productivity.
Lakes also undergo physical aging over time. A lake can become filled with sediment and particulate matter causing it to become shallower. The two main factors that control natural lake succession are the mean depth of the lake and the addition of nutrients from the surrounding drainage basin. Over time a lake will become filled in with sediments and particulates deposited from in-lake processes and those carried by inflowing waters and deposited. Eventually over time a lake can transition into a wetland or even to a dry land environment.
Lakes can age prematurely due to human influences on the lake’s natural aging process. Eutrophication caused by human influences typically occurs over decades and results in the excess growth of algae and plants, diminished lake clarity, light penetration and oxygen concentrations which can have impacts on aquatic life and the use and enjoyment of a lake. (Figure 1)