With new legislation proposed to protect and restore the waters of the Long Island Sound, Connecticut and New York lawmakers are hoping to reverse the effects of decades of over-development and pollution.

The Long Island Sound Restoration and Stewardship Act would combine two water quality and shore restoration programs to be funded at, respectively, $40 million and $25 million per year through 2020. It was introduced by U.S. Sen. Kirsten Gillibrand (D-NY) on Monday.

Co-sponsoring the bill are Sens. Richard Blumenthal and Chris Murphy, both Connecticut Democrats, who called the Sound the “most valuable natural resource” of the region.

The Sound brings in billions yearly from sport and commercial fishing, boating, recreation and tourism.

“For the millions of people who rely on Long Island Sound for work and recreation each year, we have an obligation to prioritize federal investments in its restoration and long-term health,” Murphy said Monday. “The Long Island Sound Stewardship Act is a meaningful first step.”

One especially threatening problem for the Sound involves increasing levels of nitrogen in the water, which can be traced back to the region’s septic tanks and cesspools along with wastewater treatment plants and fertilizers used on nearby lawns. The excess of nutrients spurs algal blooms, upsetting the balance of oxygen in the ecosystem and resulting in “die-offs” to which thousands of turtles and fish fall victim.

In one such die-off that began in late spring, tens of thousands of dead bunker fish, or Atlantic menhaden, washed to the shores of Eastern Connecticut and Long Island.

“It’s the biggest problem, really, because it so fundamentally changes the ecosystem,” said Judy Preston, the Connecticut outreach program coordinator for the Long Island Sound Study, an Environmental Protection Agency program that researches water quality of the Sound. “Once you’re dealing with oxygen and the ability of the ecosystem to maintain itself, that’s pretty serious.”

In early June, the National Fish and Wildlife Foundation found that human activity was causing the harmful release of pollutants like fertilizers, pesticides and herbicides into the water. Days later, a report by the University of Maryland Center for Environmental Science rated the majority of the Sound between ‘F’ and ‘C’ in rankings on phosphorus, a pollutant seen in lawn fertilizers that can kill marine life.

The effort to restore the watershed traces back to 1985, when Congress allocated funds for the Long Island Sound Study. In 2006, Congress passed the Long Island Sound Stewardship Act, which has provided more than $3.8 billion in funding to restoration projects to date.

By continuing funding for ongoing cleanup projects, the new act aims to build on these efforts.

“This critical measure will ensure the preservation, restoration and maintenance of the Long Island Sound,” Sen. Blumenthal said. “I am proud to join with my colleagues from both sides of the aisle in supporting this legislation to ensure that the Sound can be enjoyed for many generations to come.”