Robert Louis Schueler, 83, who worked from 1971 to 1979 at the National Marine Fisheries Service and retired as deputy chief of environmental assessment, died July 28 at Holy Cross Rehabilitation and Nursing Center in Burtonsville after a heart attack. He lived in Silver Spring.

From 1980 to 1992, Mr. Schueler did part-time environmental review work for the Maryland Department of Natural Resources.

He was a native of Brooklyn, N.Y., and a graduate of the City College of New York. He also was a graduate of what is now State University of New York College of Environmental Science and Forestry at Syracuse University, where he received a master's degree in wildlife management.

Mr. Schueler worked as a biologist in water resources for the U.S. Fish and Wildlife Service and the Bureau of Commercial Fisheries across the country before settling in the Washington area in 1971.

He served in the Marine Corps in the Pacific during World War II. He received the Silver Star for his actions on Iwo Jima while serving as an artillery forward observer in early March 1945.

Despite being wounded severely, he exposed himself to enemy fire constantly to attain the best positions as an observer and thereby aid fellow Marines. He stayed in the job until a replacement arrived.

He was in the Marine Corps Reserve until 1974 and attained the rank of colonel.

Mr. Schueler was a member of St. John the Baptist Catholic Church in Silver Spring. He did volunteer work at the church as well as for the conservation group Trout Unlimited and the Potomac River area chapter of the American Fisheries Society.

Survivors include his wife of 52 years, Frances Nash Schueler of Silver Spring; a daughter, Jennifer Schueler, known as Sister Veronica, a nun in the Catholic order of the Franciscan Sisters of the Eucharist, of Meriden, Conn; four sons, Carl Schueler of Colorado Springs, Vincent Schueler of Olympia, Wash., Thomas Schueler of Ellicott City and Timothy Schueler of Gaithersburg; two brothers; and seven grandchildren.