How Passenger Vessels Affect Park Waters

Image from the National Park Service's page.

Passenger vessels — ferries, guided water tours, airboats and cruise ships — take visitors to parts of the National Park System that would otherwise be hard to reach. Ferries carry and guide visitors at parks including Golden Gate National Recreation Area, Channel Islands National Park, Statue of Liberty National Monument, Cape Lookout National Seashore, Dry Tortugas National Park, Isle Royale National Park and Glacier Bay National Park. Like any form of transportation, they affect the environment around them.

Invasive species

Invasive species range from noxious weeds and feral cats to insects. Aquatic invaders, the "hitchhikers" that ride on boats and gear, are a serious threat to any ecosystem they reach, and marinas and docks are among their hot spots. Vessels can carry invaders and speed their spread from place to place, so any boat that moves between bodies of water must be properly cleaned. InvasiveSpeciesInfo.gov lists the aquatic invaders in each area.

Vessel strikes

A vessel strike is any collision between a boat and a marine animal. Whales and sea turtles are especially at risk because they surface to breathe. A strike can seriously injure or kill the animal and damage the boat or hurt people aboard. To help prevent strikes:

• watch for signs of wildlife, such as blows, dorsal fins and wings;
• slow down where wildlife is known to occur;
• stay at least 100 yards from wildlife when possible;
• wear polarized sunglasses, if possible, to see animals in the water better.

Boat traffic can also degrade habitat that supplies larger marine animals' food, and the changes vessels and people bring can alter animal behavior and migration. NOAA Fisheries has more on vessel strikes.

Plants and the water

Ferries entering and leaving marinas and piers, anchoring or stirring the water near shore disturb mud and vegetation, which can lead to algae overgrowth and the loss of natural habitat. Shallow underwater meadows store carbon and give aquatic life nutrients, shade and food.

Emissions from passenger vessels also raise the amount of carbon dissolved in the ocean, making seawater more acidic. This ocean acidification harms small organisms that matter greatly to the ecosystem, such as corals, mussels and small crustaceans. Planting native plants in and around marinas adds biodiversity and keeps the ecosystem healthy: trees and native plants, on land and in the water, take up carbon dioxide and help offset the greenhouse gases ferries release.

Fuel and oil spills

Large vessels carry fuel and oil that must be handled carefully to avoid spills that harm the environment, wildlife and people. Concessioner staff should have standard fueling procedures and know to:

• know the capacity of the fuel tank;
• work out how much fuel is needed before filling;
• never top off the tank;
• make sure whoever fuels the boat knows which deck fill is for fuel;
• use a colored cap on the fuel deck fill so it stands out from water and other fills.

Every vessel must carry a spill response kit, which may include absorbent pads and socks, protective equipment such as gloves and goggles, and a container and bags for contaminated material. Kits vary with the water environment; the Environmental Protection Agency (EPA) has more on spill prevention and planning.

Greywater

Ferries produce sewage and greywater, the wastewater from sinks, tubs, drinking fountains and wash basins. Greywater sounds harmless next to sewage, but it contains oils, detergents, heavy metals and fecal particles. It can spread disease-causing bacteria, use up oxygen and raise nutrient levels, harming ecosystems and marine life; EPA has found it can be as contaminated as raw domestic sewage. Operators can reduce the harm by:

• installing water-saving fixtures such as low-flow sinks and shower heads;
• choosing non-toxic cleaning products for the vessel;
• fitting sink strainers to catch food and debris before they reach the greywater tank;
• keeping holding tanks in good repair and pumping them out on shore.

Discharging raw sewage into the ocean is illegal. Greywater rules depend on the type of vessel, and there are currently no federal greywater rules for recreational vessels. Park concessioners must follow their contracts and local laws on greywater and sewage. EPA answers common questions about vessel sewage.

Sources

• National Park Service: "Environmental Impacts of Vessel Operations."