A federal lawsuit filed Jan. 27 by environmentalists could hinder the Navy’s ability to conduct training exercises in the Pacific. In the suit, several organizations state that the Navy’s use of high-powered sonar and explosives during exercises planned for the next five years will harm marine mammals. The exercises, as such, would violate the Marine Mammals Protection Act, the environmental groups, spearheaded by the Natural Resources Defense Council, stated in court papers. The exercises in question would take place in waters extending from southern California to Hawaii, which are home to several species of whales.