Overall, phosphorus concentrations vary more in the summer than winter. Nutrients, like nitrogen and phosphorus, occur naturally in water, soil and air. Just as the nitrogen and phosphorus in fertilizer aids the growth of agricultural crops, both nutrients are vital to the growth of plants within the Bay. Excess nutrients, however, are pollutants. Sewage treatment plants, industries, vehicle exhaust, acid rain, and runoff from agricultural, residential and urban areas are additional sources of nutrients entering the Bay.
Nutrient pollution is the number one problem in the Bay system.
Excess amounts of nitrogen and phosphorus cause rapid growth of phytoplankton, creating dense populations or blooms. These blooms become so dense that they reduce the amount of sunlight available to underwater Bay grasses. Without sufficient light, plants cannot photosynthesize and produce the food they need to survive. Algae also may grow directly on the surface of Bay grasses, blocking light. Another hazard of nutrient-enriched algal blooms comes after the algae die.