Nutrients in Mountain Lakes: How Much Is too Much?

Abstract

Yosemite, Kings Canyon, and Sequoia national parks protect over 1,200 mountain lakes. These lakes provide healthy homes for plants and animals and supply clean water to downstream communities. These clear blue lakes are high up in the mountains, where they receive very low amounts of nutrients from the watershed. Nutrients help living things grow and be healthy. However, human activities from communities upwind are adding nutrients into the air. These nutrients travel on air currents to remote watersheds via rain, snow, and dry particles. They increase lake algae growth, which disrupts the balance of plants and animals. We conducted experiments to determine the amount of nutrients it takes to increase algae growth. We compared these levels to current lake nutrient concentrations and found that over half of the lakes had concentrations that were below the determined early warning point and just under half were at levels of higher concern.