Aquarium shuts down for a day after glass cracks in giant tank

“Oh, no, you’ve got to be kidding,’’ said Deborah Bowen of Falmouth, 57, who was stopped at the door with her 11-month-old granddaughter Pilar strapped to her chest in a BabyBjörn. “She loves the fish in the big tank.’’

Before the aquarium opened in the morning, staff discovered the spiderweb-like fracture on the inner pane of a 2-inch-thick laminate window, comprising three separate sheets of glass. It was not immediately clear what caused the break in the 200,000-gallon tank, home to a coral reef and more than 750 creatures including Myrtle, a 560-pound green sea turtle who has lived there since June 1970.

“There’s been no leakage and no damage to any animals,’’ said Jane Wolfson, an aquarium vice president. “It’s just a crack.’’

Staff would not allow reporters to inspect the window or observe repairs, which were expected to be completed in time for the facility to open today. But that was little comfort for yesterday’s visitors. An average of about 2,000 people visit the aquarium daily.

A group of seventh graders from Basalt Middle School in Colorado milled about outside the aquarium while chaperones made arrangements for a detour to the Museum of Science.

“They were all bummed,’’ said Mary Watson, a teacher at the school near Aspen. “They were excited about going inside. They wanted to see the penguins.’’

It marked the fifth time in the last four decades that a crack developed in one of the tank’s 63 windows. The aquarium estimated that it lost $30,000 to $40,000 in revenue yesterday because of the closure, only a fraction of its $40 million annual budget. The repairs are expected to cost between $10,000 and $20,000.

“It’s a big event when this happens, but it’s not an unheard-of event,’’ said Tony LaCasse, the aquarium’s media relations director. “It’s something that we have emergency procedures around which kicked in right away this morning.’’

The window that broke is roughly 4 feet wide and 6 feet tall. It was at the top lip of the tank, well out of reach from concrete ramp that twists around the exhibit like a cork screw, according to James Duffey, the facility’s director of project management and design. Staff was still trying to determine what caused the break, but it seemed unlikely that it was the work of an angry shark or ornery turtle.

“We have animals run into the glass all the time,’’ Duffey said.

To fix the window, workers drained more than 6 feet of water from the aquarium, which is 23 feet deep. None of the animals had to be removed. A solid opaque panel was installed temporarily until a permanent glass replacement could be made. By yesterday afternoon, water was being added back to the tank.

The location of the window at the top of the exhibit made repairs easier than the past, including the most memorable break in the early 1980s, which was much lower in the tank.

“There is a famous incident involving a TV station that will go unnamed,’’ said LaCasse, recalling that the crew had ignored warnings to keep a hot light away from the tank’s windows. “There was a distinct pop on one of the pieces of glass.’’

LaCasse continued, “It was much lower in the Giant Ocean Tank. It was a much bigger challenge having to move animals. That didn’t happen today.’’

Andrew Ryan can be reached at acryan@globe.com.