Marina and boating activities can introduce many different types of pollutants into the coastal environment. Scientists have found these pollutants can reach harmful concentrations in the water column, sediments, and tissues of organisms inhabiting the marine environment. Improper marina siting and design can also damage the coastal environment.
Low Dissolved Oxygen: Untreated sewage discharged from recreational boats and fish wastes discarded into the water body deplete dissolved oxygen levels as they decompose. Fish and other aquatic organisms need dissolved oxygen in the water to survive; they suffocate without enough oxygen. Low levels have resulted in fish kills.
Metals: Metals such as lead, copper, arsenic, zinc, and tin and metal-containing compounds, have many functions in boat operation, maintenance, and repair. Common metal containing products include: gasoline, anti-fouling paints, pesticides, and wood preservatives. Metals can enter the waterways during uncontrolled pressure washing, painting, or fueling activities. The metals then accumulate in the sediments and water column. Metals can be toxic to marine organisms resulting in death, or chronic impairments such as deformity, reduced fertility, and reduced species diversity.
Oils: Oils and other petroleum products can enter the aquatic environment during refueling and bilge or fuel discharge from boats. Oils are poisonous to marine organisms. Oils coat bird's feathers, preventing them from flying or staying warm. Petroleum products can also cause cancer and impair immune response in fish and other aquatic life.
Bacteria: Many scientific studies have shown that boats and runoff from marinas can be a significant source of fecal coliform bacteria in areas of high boat density and poor water flushing. High bacteria concentrations are a public health threat. People can contract diseases or even die from coming into contact with contaminated waters or by consuming shellfish from waters with elevated bacteria levels. High bacteria concentrations have closed shellfishing areas and swimming beaches near marinas.
Reduced Water Flushing: Marinas that restrict water flushing and movement can contribute to low dissolved oxygen levels and a build-up of toxic compounds.
Disruption of Sediment and Habitat: Inappropriate boat operation and dredging can destroy habitat, resuspend bottom sediment, and reduce water clarity. Constructing marinas, ramps, and related facilities can physically alter or destroy wetlands, shellfish beds and other bottom communities. Resuspending bottom sediments during dredging often reintroduces toxic substances into the water column. As the sediments settle back down, they can bury benthic organisms, suffocating them. Cloudy, or turbid water, blocks light from reaching aquatic plants, such as submerged aquatic vegetation (SAV), reducing their photosynthetic activity. SAV provides valuable habitat for many important fish and shellfish, such as crabs.
Shoaling and Shoreline Erosion: Shoaling and shoreline erosion result from physical transport of sediment due to waves and/or currents. Increased boat traffic can cause unnatural wave action that erodes coastal shorelines, introducing added sediment into the water column.