The Seattle City Council voted unanimously Monday to cement a $34 million contribution toward the construction of a Seattle Aquarium expansion project.

The nonprofit Aquarium Society, which operates Seattle’s city-owned aquarium, intends to build a $113 million new Ocean Pavilion between Pike Place Market and Piers 59 and 60 as part of a wider effort by the city to remake the downtown waterfront after the removal of the Alaskan Way Viaduct.

The society’s plan calls for the new structure to feature a 325,000-gallon tank with sharks, stingrays and fish from the South Pacific’s Coral Triangle area.

Aquarium leaders contend the pavilion, which could open as early as 2023, is needed to supplement long-standing exhibits on Piers 59 and 60. The leaders say the addition will help the aquarium welcome hundreds of thousands more visitors each year and educate them about global marine conservation.

Monday’s action will authorize funding and construction agreements between the city and the society, which has promised to raise $60 million in private donations and $19 million in other public funds. Seattle’s contribution is slated to come from real-estate excise tax revenue, which is used for capital projects.

The city plans to build a park-like ramp over a rebuilt Alaskan Way to connect the hillside market with the Ocean Pavilion and a new promenade.

Monday’s vote was 8-0, though Councilmember Mike O’Brien noted that public opinion could at some point turn against keeping certain animals in captivity.

Adding to the aquarium expansion is “a long time coming and the right thing to be doing,” said Councilmember Sally Bagshaw, whose District 7 includes downtown.