Sediment Load:
18.7 billion pounds of sediment are estimated to flow into the Bay's rivers and streams. Erosion and sedimentation occur naturally; however, land that has been cleared for agriculture can drastically increase the rate of erosion because the land is less efficient at slowing and absorbing water. This "run-off" flows quickly across surfaces, carrying sediment and nutrients, directly into rivers and ultimately, the Bay.
Sediment in the Bay decreases water clarity, and adversely affects the health of sea grasses and the fish and crabs that live in them. Sediment directly hurts bottom-dwelling organisms like oysters. It smothers them and makes filter feeding more difficult. 60% of sediment comes from an agricultural source. |
|
Nutrients:
Animal manure and poultry litter contribute about half of the Bay's agricultural nutrient load. There are two major nutrients: Phosphorus and Nitrogen. Combined, these two nutrients fuel algal blooms in the Bay. Algal blooms can reduce the amount of light penetrating the water, having a similar negative effect as excess sediment. Algal blooms also end in massive die-offs, which are then decomposed. In the process of decomposition, oxygen in the water becomes depleted. The number of hypoxic and anoxic regions of the Bay is increasing each year.
As the graphs indicate, manure produced by livestock is responsible for approximately 17% (43 million pounds) of the total Nitrogen load and 26% (4.8 million pounds) of the total Phosphorus load. |
