- Excess nutrients are added to the Chesapeake Bay when human and pet waste, fertilizer and deposits from car exhaust find their way into the water. The nutrients in these waste products encourage the growth of algae. When alga populations grow too high, the water becomes cloudy, blocking needed sunlight from reaching bay grasses and reducing their ability to perform photosynthesis. Light is reduced further when algae coats grass leaves.
- Storm water runoff contains sediment and chemical contaminants that pose a danger to bay grasses. Storm water runoff produces more contaminants than industries, federal facilities and waste water treatment plants, according to the Chesapeake Bay Program, a group that’s been working to restore the area since 1983. Pollutants come from many sources, including car leaks, lawn fertilizers and pet wastes, and drain into the Bay from local waterways and storm drains. Activities that increase runoff include clearing vegetation, removing and compacting soil, and building roads and parking lots. Storm water runoff erodes stream banks and puts sediments into the water that reduce the amount of sunlight available for bay grasses.
- Invasive plants, like the water chestnut, threaten native bay grasses and create places for mosquitoes to breed. They also interfere with water recreation because their hard, 1/2-inch-long spines can penetrate shoes and discourage people from using beaches. According to the Maryland Department of Natural Resources, 1 acre of water chestnuts produces enough seeds to cover a 100-acre area the following year. Water chestnuts are native to Asia but can be found throughout the northeast and as far south as Maryland. Between 1997 and 1999, approximately 50 water chestnut plants were able to spread and cover a 30-acre area of the Bird River. In 2010, the Lloyds and Turners Creek areas started showing a large increase in water chestnuts.
- Some animal species have caused substantial damage to bay grasses by feeding on their leaves, stems and seeds. Mute swans are a particular problem. One adult mute swan can eat 8 pounds of bay grass every day. The cow nose ray is a type of fish that also causes substantial damage to bay grasses. High water temperatures, such as those experienced in 2005, can kill eelgrass, one of the 15 species of bay grass that inhabit this region. Eelgrass doesn’t grow any farther south than the Chesapeake Bay, so warmer than average temperatures can severely impact it.
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