The natural aging of a lake through nutrient enrichment is a biological process called Eutrophication. Over hundreds or thousands of years, a "young" lake with clear, low-nutrient water (known as Oligotrophic) naturally accumulates silt and organic matter from the surrounding landscape. As nutrients like phosphorus and nitrogen build up, the water becomes more fertile, supporting an increased growth of algae and aquatic plants. This transition moves the lake into a Mesotrophic state and eventually into a Eutrophic state, where the water is murkier and highly productive. In the final stages of this natural lifecycle, the excessive organic matter decays, consuming oxygen and potentially leading to "dead zones" where fish cannot survive. Eventually, the lake fills with sediment and transforms into a marsh or wetland, and finally into dry land. While this is a natural geological process, human activities like fertilizer runoff can cause "cultural eutrophication," which dramatically accelerates this "aging" process from centuries down to mere decades, often causing severe ecological damage.