September 2006 marked the discovery of the largest dead zone in the history of Hood Canal. The dead zone may have been caused by low oxygen levels due to algal blooms. Algal blooms occur in part because of warm weather and the slow turnover of water in the southern end of the canal, causing the build-up of nutrients from fertilizers and leaky septic systems. Organic matter, brought in by ocean water and certain trees, could additionally be contributing to the high nitrogen levels in the basin. Excess nutrients and organic matter causes a body of water to lose oxygen, through a process called eutrophication. In Hood Canal, eutrophication has led to unwanted algae blooms. Nitrogen combined with sunlight triggers algal growth. A lack of sufficient consumers has resulted in a mass overgrowth of algae in the basin. When the algae die, bacteria feed and their populations explode, robbing the water of oxygen. A state of hypoxia is created.