An Environmental Protection Agency official says the agency realizes Chesapeake Bay watershed states will have to make tough decisions to meet new pollution limits. EPA Regional Administrator Shawn M. Garvin made the comments last week as the federal agency issued limits for two nitrogen and phosphorus. The EPA set annual limits of 187.4 million pounds of nitrogen and 12.5 million pounds of phosphorus for the six-state bay watershed. That is down from 247.5 million pounds of nitrogen and 16.62 million pounds of phosphorus last year. Pennsylvania, the source of about half of the bay’s fresh water, received the biggest allocations. Nitrogen and phosphorus spur oxygen-robbing algae blooms and come from sources including fertilizer, sewage, and detergents.