Over the last two years, filmmaker Barbara Ettinger and her husband, Sven Huseby, have regularly left the comforts of their Germantown home, traveling to universities and Arctic field stations to chronicle the imminent danger to marine life posed by carbon dioxide emissions from power plants, automobiles, barbecues, and furnaces — the same forces that are causing global climate change. Ettinger’s recently released film A Sea Change documents this problem, which is known as ocean acidification. While greenhouse gases trapped within the earth’s atmosphere are causing temperatures and sea levels to rise, carbon pollution falling into the oceans is changing the chemical composition of sea water and threatening the viability of the entire marine food chain.Ettinger’s film depicts the beauty of ocean life and the devastating threats it faces, and puts a human face on highly complex technical issues that, handled differently, could go right over most audiences’ heads. Scientists explain in plain English that the carbon pollution raining down on our oceans is changing the water’s acidity and destroying the protective shells of tiny organisms known as pteropods, a key link in the aquatic food chain. One expert plaintively notes that, in the Gulf of Alaska — one of the nation’s most productive salmon fisheries — the shells of these creatures are already dissolving in about 48 hours. An economist explains that we risk destroying global commercial fishing industries worth $60-$100 billion per year. And Huseby, who serves as the film’s narrator, struggles to figure out how to break the news to his six-year-old grandson that the Earth’s resources he will inherit are damaged goods.While President Obama has made climate change one of his top priorities, environmental advocates are concerned that legislation to cut carbon emissions has taken a back seat to the campaign for healthcare reform. Marine scientists fear delay could be fatal to marine life. The current level of carbon dioxide in the atmosphere, 387 parts per million, is dangerously close to a tipping point of 400 parts per million, a level they fear will unleash vast environmental damage in the marine world (with one scientist predicting a “mass extinction event”).For Hudson Valley residents, the risk to our oceans is a backyard issue. The Hudson River is an estuary, an arm of the sea. A study by the environmental group Riverkeeper shows a decline in Hudson fish populations since the 1980s in 10 out of 13 fish species. While the report does not link the problem to ocean acidification, it sends a message that action to address the range of threats to our oceans and rivers should be a priority for all of us. Scenic Hudson is working to stem this problem through habitat protection and restoration projects and through litigation aimed at forcing power plants to modernize their obsolete water cooling systems that withdraw billions of gallons of Hudson River water each day, causing massive fish kills.While the U.S. House of Representatives has passed legislation that would begin to address both climate change and, as a result, ocean acidification, the Senate has yet to act. Ettinger’s film is a must-see primer on the issue aimed at inspiring urgent action — to reduce our own carbon footprint, and to call on our legislators and president to immediately tackle the problem — before it is too late.Ned Sullivan is president of Scenic Hudson and former environmental commissioner of the State of Maine.