What is the environmental impact of sewage from boats and ships on our waterways?

What is the environmental impact of sewage from boats and ships on our waterways?

— Eileen Macaw, Traverse City, MI

There is a clear relationship between the number of boats in a given area and the levels of coliform bacteria in both water and shellfish, reports the San Francisco Estuary Project. High levels of coliform bacteria, which indicate sewage pollution, can spread disease, contaminate shellfish beds and decrease oxygen levels in the water. Studies on swimmers, scuba divers and windsurfers show the effects of contact with bacteria-infested waters, which include nausea, vomiting and diarrhea. Individuals may also become ill by eating shellfish that have consumed human sewage.

Even coral reef communities are affected when high bacterial levels cause an overgrowth of aquatic plants and algae. Dead zones, like the one currently in the Gulf of Mexico, are areas of the ocean starved of oxygen because sewage has spurned robust algae blooms that consume all available oxygen when they die and decompose. Fish and plants can no longer survive in these areas.

According to the Oceans and Coastal Protection Division of the U.S. Environmental Protection Agency (EPA), slow-flowing rivers, lakes, marinas and “other bodies of water with low flushing rates” are particularly susceptible to the havoc brought on by boat sewage. To counter the problem, in 1998, the Federal Clean Water Act allowed states to designate all or portions of their bodies of water as no-discharge zones. These zones help to ensure that public drinking water is not contaminated. Currently, six states have adopted the policy. The act also regulates standards for marine sanitation devices—boat toilets. Such legislation aims to improve the quality of water at recreation sites for both human and aquatic life.

One of the largest waterway polluters is the cruise ship industry, which often dumps raw sewage directly into the sea. According to Jackie Savitz, Pollution Campaign Director and Senior Scientist for the Washington, D.C.-based nonprofit organization, Oceana, the cruise ship industry alone discharges tens of thousands of pounds of sewage a day into some of the most pristine parts of the ocean. The extent of the effect of such pollution depends on where you are, she explains. In more sensitive ecosystems, such as in Alaska and Hawaii, cruise ship sewage is a huge percentage of the water pollution problem, where other sources, such as sewer overflows, may have more of an impact on water quality in places such as New York. Discharge into the ocean by cruise ships is not covered under the Clean Water Act, but states can take action. Alaska was the first to pass a law requiring tougher standards for cruise ships, says Stavitz.

Oceana recently targeted Royal Caribbean to pressure them to clean up their dumping practices. After an 11-month campaign, during which some 90,000 people signed a pledge to not sail with Royal Caribbean until it took action, the company agreed to adopt sophisticated wastewater treatment technology to treat sewage on board, and is now installing systems throughout its entire fleet.

CONTACTS: San Francisco Estuary Project, (510) 622-2465, www.abag.ca.gov/bayarea/sfep; U.S. Environmental Protection Agency’s Oceans and Coastal Protection Division, (202) 260-1952, www.epa.gov/owow/oceans; Oceana, (202) 833-3900, www.stopcruisepollution.com.