South Street Seaport, the area of Manhattan shoreline just south of the Brooklyn Bridge, is in play, and what happens over the next few months will set its future for decades.

The opportunity is a result of two shifts in real estate: A year ago, General Growth Properties, a major publicly traded REIT that owns or operates 200 shopping malls nationwide, acquired the Rouse Co., including the South Street Seaport properties that it developed – Pier 17 and four other assemblages – a total of 385,000 square feet of retail space.

And a half year ago, the city relocated the 180-year-old Fulton Fish market to the Bronx, leaving behind an estimated 140,000 square feet of vacant selling space. GGP intends to exercise its option to acquire the city-owned landmarked “Tin Building” as well as a block of privately owned market stalls that were also vacated.

A spokeswoman for GGP, Cheri Fein of Rubenstein Associates, said the developer plans “to service the growing residential population as well as the people that work there.”

The city’s Economic Development Corporation will now have to decide how to develop its remaining parcel, the non-landmarked “New Market Building.”

The city’s planning commissioner, Amanda Burden, is effusive about the possibilities. “South Street Seaport is unique in New York City. It’s unique among all American cities,” she said. “The wonderful scale, the texture, with access to the water and a view of the Brooklyn Bridge.”

It’s a treasure for the city, she said – “and an important amenity for the financial district – their respite and recreation.”

The seaport is where 200 years ago New York became a great global city through innovations in technology, financing, and business models, the latter best exemplified by the initiation of the world’s first scheduled cargo shipping line, leaving on time, and half empty, in a January snowstorm.

The City is developing three plans for downtown, all involving South Street Seaport. All three of them have good prospects for being accomplished.

The Mayor’s Harbor District links Brooklyn Bridge Park, Governor’s Island, the Battery-Statue of Liberty, and the South Street Seaport by water – with the Seaport an obvious embarcadero for ferries.

In addition, the city’s planning department and the Lower Manhattan Development Corporation have created the Fulton Street Revitalization Plan, an upgraded corridor from the Hudson River to the East River, encompassing the new World Trade Center and the new Calatrava Transit Hub, and culminating with a park at the old Burling Slip in the South Street Seaport.

Most ambitious of all is city planning’s East River Waterfront Esplanade and Piers Project, with $150 million of LMDC funds earmarked to create a two-mile walkway-bikeway along the entire tip of Manhattan. Innovations include enlivening the dreary underside of the FDR Drive with lighting, traffic-muting cladding, and pavilions for community, culture, and commerce. At the South Street Seaport section, the dismantled Pier 15 will be rebuilt as a public open space, to be used for historic vessel tie-ups.

Peck Slip, where huge oceangoing sailing vessels once pulled in for unloading is now a cluttered parking lot. But under the city’s plan it will become a great plaza. The north side of Pier 17, now neglected, but breathtaking in its sweep of the East River, will become a small boat marina.

Civic groups have been actively engaged in shaping the course of the South Street Seaport. SeaportSpeaks, an energetic group composed of residents, architects, preservationists, developers, builders, cultural leaders, residents, and government officials, convened a one-day charrette, a workshop to develop ideas. The charrette’s 70 participants agreed that the Ssaport’s scale, texture, sense of history and maritime connection have to be preserved and promoted to attract unique, appropriate retail.

“With the removal of the Fulton Fish Market, cultural institutions and venues become the living, working link to the Seaport’s rich narrative,” said the co-chair of SeaportSpeaks, Lee Gruzen. “They should be the honey to attract New Yorkers to come, stay and return again and again.”

The charrette’s conclusions are available on the group’s Web site, seaportspeaks.org. They include ideas like “Attract the finest restaurateurs-seafood first – as better quality restaurants will be an attraction.” And “Put the SEA back into the SEAport.” And create a “real neighborhood” with groceries, food, and shopping, so that residents of the neighborhood “don’t have to leave.”

The main issues are maintaining the momentum and creating an entity to coordinate agencies, lobby for funds, guide development, oversee spending, and assure businesses get the services they need. Right now the civic groups are thrashing out governance options, whether a Local Development Corporation, an Economic Development Corporation Task Force, or other public private structure, to sustain the enterprise and keep alive at the seaport the spirit and energy that were there when it began.

Ms. Weisbrod is president of the Partnership for Sustainable Ports and a member of the steering committee of SeaportSpeaks.