The extensive watersheds of the Caloosahatchee (1,400 square miles) and Lake Okeechobee (4,400 square miles) each contribute water that flows into the Caloosahatchee estuary and the Gulf of Mexico. Water quality is affected by both Lake Okeechobee discharges and runoff from the Caloosahatchee watershed. Over time, these watersheds have changed from low-nutrient loading marshes and wetlands to high loading urban and agricultural land uses. Nutrients increase turbidity and decrease concentrations of dissolved oxygen (DO). In addition, excess nutrients fuel nuisance algal blooms. Losses of low-nutrient adapted communities, such as seagrasses have contributed to changes in fish, crustacean and marine mammal communities.