Your Role in Protecting the Ponds of Nantucket

We are all responsible for keeping out ponds clean. The ponds on Nantucket provide many benefits to those living near them. As sources of potable water, habitats for fish and wildlife, and the recreation they provide, these waterbodies are invaluable.

Environmental conditions on the island, such as permeable sandy soils, a sole source aquifer, and significant rainfall, make these ponds particularly sensitive to contamination and degradation. Water quality problems can occur as the result of pollution from septic systems and runoff from lawns and street.

Therefore, it’s important for everyone to do their part in protecting the quality of the ponds they live near.


Phosphorus is an element that is found naturally in soil, rock and other organic material. It is a necessary nutrient for plant growth and for this reason, works well as a fertilizer. Phosphorus is a threat to water quality in ponds because it stimulates aquatic plants such as algae to grow as well.

As the level of phosphorus increases, algae will continue to multiply. When these algae eventually die off, they settle out in the bottom of the pond where they decompose.

The process of decomposition requires oxygen. An excessive amount of algae will therefore deplete the oxygen levels in a pond. The depletion of oxygen can cause the death of some fish populations. High phosphorus levels and the subsequent algal blooms are also responsible for decreasing water clarity and producing foul odors.

Human activities contribute a great deal to the phosphorus loading that takes place. The human activities that add major sources to phosphorus to ponds are failing septic systems, the use of phosphorus-containing detergents and dish-soaps, runoff related to roads, land development and alteration of the vegetation or lay of the land around them.

Phosphorus loading can be minimized by maintaining an effective septic system, leaving, or planting additional vegetation between your home and the shoreline as a “buffer”, preserving the existing ground features, preventing runoff from flowing freely into the pone and practice erosion control where necessary.


Algae are microscopic plants that grow natural ponds. Algae have the potential to grow to an enormous population, called an algal bloom. Algal blooms can turn water a cloudy green or brown, and can appear as thick, green, slim that float on the pond surface. Excessive algae pond can make that water look murky, damage habitats of fish and other aquatic species, and produce noticeably foul odors.

Under certain conditions, some blue-green algae (named for the pigment in its cells) can be toxic. Such conditions include: warm water temperatures, a neutral pH, and high levels of nutrients in the water. These toxins can be dangerous to pets, livestock, waterfowl, and other animals and can also be harmful to humans (see Health section).

Although we can’t control the temperature or pH a pond, we can limit the amount of nutrients (phosphorus) entering the pond, which would effectively prevent many algal blooms from occurring. Ensuring that your septic system is operation correctly, diverting prevent algal blooms in your pond.

Hazardous Chemicals

A wide variety of the products commonly found in our household are considered hazardous materials and care needs to be taken when disposing of them. These products can impact human health, health of the nearby wildlife, and that of our pond. Special care should be taken in storing and handling these products. Used motor oil, pesticides, paint thinners and other chemical products should be stored in a dry, contained area to prevent spilling. Leaving the labels on the containers so they can be easily identified. Be careful not to spill these products on the ground. Just a little bit of these substances can go a long way towards contaminating your soil, groundwater and pond. When possible, less toxic products should be used.

Hazardous materials need to be disposed of properly. If these products are poured into your toilet, down the drain or on the ground they will make their way into the ground water, the pond and maybe your drinking water. Most towns have special collection days to help you get rid of your unwanted hazardous materials in a safe manner. Call your Board of Health for information on these programs.


How Your Health Can Be Affected

The water quality of the pond that you bathe or boat in can directly affect your health. Several studies have been conducted which have related the presence of pathogens (i.e. disease-causing microorganisms) to the occurrence of adverse health effects in swimmers. The pathogens associated with human fecal matter typically cause gastroenteritis and may be present in the water as a result of a failing septic system or disposal of sewage by boats. Among the health effects observed in studies we gastrointestinal symptoms (e.g. vomiting, diarrhea, stomach-ache, nausea), respiratory symptoms (e.g. sore throat, cough, chest old, runny nose, sneezing), eye and ear symptoms (e.g. infections, earache, itchiness), dermal symptoms (e.g. skin rash) and fever.

Under certain conditions, some algae produce toxins that can harm those swimming in the water containing the toxins. The effects of these toxins that have been identified in humans include skin and eye irritation, dizziness, indigestion, cramps and vomiting.

Another health issue Nantucket residents should be aware of is Lyme Disease. The tall greases and shrubs growing along ponds that are beneficial to the water quality of the pond are also the preferred habitat of deer ticks, the bite of which can cause Lyme Disease.

When walking in grassy or wooded areas, cover exposed skin with clothing and tuck pant bottoms into socks. Apply an insect repellent containing DEET (to clothes & body) or permethrin (to clothes only). Perform daily tick checks of yourself and your family. You may also want to discuss the benefits of the Lyme Disease vaccine with your doctor.

The Nantucket Watershed

A watershed includes all of the area that contributes surface water or ground water to a pond and lake. Each watershed is delineated by connecting the points of highest elevation around the waterbody. The Nantucket watershed is characterized by permeable, sandy soils and a sole source aquifer, the Nantucket Aquifer. This aquifer is the primary source of drinking water for Nantucket residents.

The streams, ponds and groundwater that make up the Nantucket watershed are all connected to one another. Because of this, water and the substances in it can travel between the ponds and groundwater. Thus, any contaminant within the watershed has the potential of affecting the water quality of the ponds as well as the drinking water source. This is why it is so important to limit the inputs of pollution at each source.