Unfortunately, it often happens: while we're swimming on a beach or in a small bay, the water becomes cloudy, darker, and we notice traces of oil and leftover garbage. What happened? A yacht, or even a boat, simply dumped its leftover food (like when we throw it in the trash after a meal).
But the water becoming cloudy and unsafe for swimmers is only one of the consequences: in reality, that boat has transformed, with this uncivilized person, into a real ecological bomb.
The most significant consequences of dumping food waste into the sea are:
- Increased nutrients in the water. The leftovers decompose, releasing nitrogen and phosphorus. In bays, ports, or areas with poor water exchange, this can encourage the proliferation of seaweed and reduce available oxygen.
- Alteration of wildlife behavior. Fish, seagulls and other animals can become accustomed to feeding on boat waste, altering their diet and natural behavior.
- Introduction of non-local species. If leftovers contain ingredients from other areas (e.g. seafood or vegetables), they may introduce unwanted microorganisms or organisms.
- Aesthetic and hygienic pollution. Floating food particles or debris accumulating near the shoreline can create unpleasant odors and attract opportunistic animals.
In particular, oil slicks at sea form because oils and many hydrocarbons have a lower density than water and are immiscible with it: instead of mixing, they float and spread on the surface, forming a more or less extensive film.
Damage increases when water used to wash floors, surfaces, dishes, or other onboard areas is discharged into the sea, as this water can contain chemicals as well as organic residues. This is a common occurrence in harbors where boats and yachts spend the night.
In this case the most serious damages are:
- Chemical pollution. Detergents, degreasers, and disinfectants may contain surfactants, perfumes, preservatives, and other substances that may be toxic to some marine organisms, especially if released into coastal or shallow waters.
- Reduction in water quality. Some components can promote foam formation or alter water properties, with effects on ecosystems.
- Nutrient intake. If wash water contains food residues and detergents containing phosphorus or nitrogen, it can contribute to eutrophication, i.e. the excessive growth of algae.
- Accumulation of microplastics. Cleaning operations can wash synthetic fibers from cloths, sponges, or fabrics into the sea, as well as small plastic particles already present in the onboard environment.
- Damage to marine fauna. Some substances can be irritating or toxic to fish, shellfish, and other organisms, especially in high concentrations or in areas where multiple discharges accumulate.
In general, household waste is considered more problematic than food waste because it can introduce substances into the sea that do not degrade quickly or that can be harmful even at low concentrations.
Finally, toilet waste, also called black water , is among the on-board wastes with the greatest potential environmental impact if released directly into the sea, especially near the coast.
The main effects are:
- Microbiological contamination. Sewage can contain bacteria, viruses, and other fecally derived microorganisms that compromise water quality and pose a risk to human health, especially in bathing areas and shellfish harvesting areas.
- Increased nutrients. Feces and urine provide nitrogen and phosphorus, which can promote eutrophication, with excessive algal growth and a decrease in dissolved oxygen.
- Reduction of oxygen in the water. The decomposition of organic matter consumes oxygen, putting fish and other marine organisms under stress.
- Deterioration of water quality. Discharges can make water cloudy, cause unpleasant odors, and compromise coastal ecosystems.
- Spread of contaminants. If chemicals are used in toilets on board (e.g. some tank additives), these can further contribute to pollution.
All boats, and yachts in particular, are now equipped with holding tanks , which collect toilet waste until it is emptied in dedicated port facilities or in accordance with regulations. Food scraps should be stored until they can be properly disposed of on land, and for water and household waste on boats, it is good practice to:
- use biodegradable and low environmental impact detergents
- limit the use of aggressive chemicals
- collect and dispose of contaminated water on land when required by law or when in port, at anchor or in marine protected areas
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