Those persons at the National Marine Fisheries Service who have recently concocted the deplorable and gruesome plan to "test" the effects of underwater dynamiting of oil rigs on marine life by subjecting caged turtles to an explosion should be fired for dereliction of duty. Apparently, the people supposed to protect our wildlife are instead dreaming up grisly schemes to slaughter it.

From the Sept. 18 news story, I gather that there is no question that most of the creatures will be killed or grieviously injured. The agency proposes then to autopsy the blast victims to see what killed them. I telephoned the agency and was told by a spokesman that the purpose of the ''research'' was to determine the impact of a blast on sea turtles. Surely there exists scientific equipment that could monitor the force of the shock waves at given distances without the carnage that will result from the proposed plan. The spokesman mentioned that oil companies are currently required to ensure that no sea turtles are within 1,000 feet of a blast. According to The Post, the proposed tests would subject turtles to blasts at one-fifth that distance.

If dynamiting an endangered species in order to save it is a representative example of the way this particular branch of the Department of Commerce sees fit to operate, I would like to suggest a way of cutting the federal budget: disband the entire agency. We and the turtles will be much better off without it. DOROTHEA S. ORMOND Washington