Section 75. The division may appoint from the office of environmental law enforcement a harbor master and assistant harbor masters who shall respectively have and exercise within the Charles river basin all the powers and authority which now appertain by law to the offices of harbor master and assistant harbor masters for the port of Boston appointed by the police commissioner of the city of Boston. The division may require such further duties of these officers, consistent with law, as the commission may deem expedient. The harbor master and assistant harbor masters shall receive the pay which may be established for the grade or rank which they respectively hold in the office of environmental law enforcement.