Handout of red and black mangrove in Miami Thomson Reuters By Zachary Fagenson

MIAMI, Fla. (Reuters) - New revelations that a long strip of protected mangrove trees were illegally razed amid preparations for the 2016 Miami International Boat Show has outraged Florida environmentalists.

The lost trees, critical to the marine ecosystem, were hacked away in mid-May by a Miami city contractor in advance of the five-day show expected to draw about 100,000 attendees and 1,500 boats.

Environmental activists said in a letter to the U.S. Army Corps of Engineers that staging the show in an environmentally sensitive region could violate a number of federal laws including the Endangered Species Act and the Clean Water Act.

The federal agency is currently weighing permits for the boat show, slated to be held next February at the Miami Marine Stadium.

"You've got sea grasses, corals, manatees, all sorts of protected birds," said Mayra Peña Lindsay, mayor of nearby Key Biscayne, one of the show's staunchest opponents.

The affluent city, on an island just outside Miami city limits, has hired a public relations firm to demand the National Marine Manufacturers Association move its event elsewhere.

But the city of Miami, which has agreed to replant the trees that could take more than five years to grow to full size, continues to support the boat show.

"It was an isolated incident," said Miami Mayor Tomas Regalado.

The more than 300 feet (90 meters) of mangroves were razed from a beach abutting the Miami Marine Stadium, a historic yet long dormant seaside venue that once hosted ocean races and concert performances on floating stages.

Nonprofit organizations and the city of Miami have been working for years to revive the stadium, which was shuttered after Hurricane Andrew in 1992. Miami earlier this year agreed to spend $16 million on an extensive overhaul.

The boat show, celebrating its 75th anniversary in 2016, also committed several million to improving the structure.

"Boaters are some of the original conservationists," said Ellen Hopkins, spokeswoman for the National Marine Manufacturers Association.

(Editing by Letitia Stein and Sandra Maler)