Mystic - Titanic discover Robert Ballard has ended his 15-year relationship with Mystic Aquarium, which has featured exhibits of his discoveries of ancient wrecks including PT-109 and the famed Titanic, as well as live remote broadcasts of his expeditions.

Ballard said Monday that his work with his Ocean Exploration Trust, coupled with that at the Center for Ocean Exploration at the University of Rhode Island, both of which he heads, is taking up much of his time.

"I couldn't keep this many irons in the fire. I had to make some decisions," he said.

Ballard said he had "a great run" at the aquarium and said his time there taught him much about how to reach the public and what people want to see after spending his earlier career in an academic setting at the Wood Hole Oceanographic Institution.

"It really taught me the business," he said about his time at the aquarium.

Ballard came to the aquarium in 2000 and was instrumental in the aquarium securing the state funding it needed to undertake a major expansion and renovation project. In return, Ballard agreed to stay at the aquarium for 10 years.

Aquarium President Stephen Coan said Tuesday that Ballard's departure is bittersweet after working closely with him for 20 years.

"But I'm really happy for him," he said. "So many things have come together for him over the past few years in terms of having the tools he needs for his research and the affiliations to support that work."

"Bob played a central role in helping make Mystic Aquarium an international institution," Coan said. "He not only established the new field of deep ocean archeology but expanded the horizons of Mystic Aquarium. He really had a tremendous impact here."

Coan called Ballard "one of the most important figures in oceanography and one of the most important explorers of our time."

He said the aquarium will continue to feature Ballard's exhibits and expeditions and will maintain a close relationship with him and the Ocean Exploration Trust.

The 72-year-old Ballard said he will continue to live in Lyme and is opening the East Coast headquarters of the Ocean Exploration Trust next month in the Deshon-Allyn house at the Lyman Allyn Museum in New London. He said he will continue working closely with the U.S. Coast Guard Academy and Connecticut College.

Ballard founded the Ocean Exploration Trust in 2008. Its ship, the E/V Nautilus, spends much of the year at sea involved in expeditions which are beamed live via the Internet back to the shore so researchers, students and others can follow the work. It's a technology that Ballard envisioned as far back as 1985, when he found the wreck of the Titanic, bringing him international acclaim. Although he said such technology would someday allow him to go on expeditions from the comfort of his living room, he went on several trips this past summer.

Ballard said that after spending 25 years in the Mediterranean and Black seas discovering well-preserved ancient wrecks, he will now shift his focus to U.S. waters, including vast stretches of the Pacific.

At a three-day December workshop in San Francisco, researchers will present proposals to the Trust for expeditions aboard the Nautilus next year, when about a dozen will take place. Ballard also plans to continue his exploration of the nation's marine sanctuaries.

He said the trust's work is not just scientific but has geopolitical and economic importance. For example, he said the Nautilus will be looking for new sources of rare earth metals, a critical material used in the manufacturing of computer components. Currently, China controls much of the world's rare earth metal supply.

"There is so much on our plate right now. We wanted to focus on the Nautilus and continue its growth," he said.

Ballard said the Nautilus has received a $15 million infusion of technology including a state-of-the-art digital mapping system of the ocean floor.

"Next to his wife, the Nautilus is the love of his life," Coan said about Ballard and the ship. "It travels the world's oceans 24/7. It's all-consuming."

Ballard said he will continue his magazine and television work with National Geographic and "Nova" and educational efforts through the JASON project and other outlets.

j.wojtas@theday.com

Twitter: @joewojtas