Nitrogen is a nutrient important to the growth and reproduction of plants, and it is considered a pollutant of concern in the Lake Tahoe Region. Nitrogen and phosphorus together support the growth of algae in Lake Tahoe. Free-floating algae occur throughout Lake Tahoe and contribute to the decline in water transparency and attached algae coat rocks in the nearshore, adversely affecting nearshore aesthetics. Landscape disturbances including, but not limited to, impervious road and parking lot surfaces, residential and commercial development, wildfire, and the degradation of stream environment zones, can contribute to sediment and nutrient inputs to the lake or its tributaries. Weather variations and their effects on stream hydrology (particularly the extremes of droughts and floods), and long-term climate change are considered among the most important environmental drivers of tributary runoff.