In the worst fish kill in Maryland in more than a decade, at least 200,000 fish have died in the past week along two tributaries of the Chesapeake Bay. Officials blamed the fish deaths on buildups of phosphorus and nitrogen, which create algae blooms that deplete oxygen in water. A drought in the area has prevented the contaminants from being flushed out of rivers and creeks by rainfall, and if the drought continues through July, as many as 1 million fish could die.