Nova Scotia’s Estuaries:

By Nicole Oliver

Estuaries are bodies of water along our coasts where fresh water from rivers flows into and combines with salt water from the ocean. In Nova Scotia, we often refer to this part of our watershed as a harbour, basin, or inlet. Whatever name we use, though, these unique and dynamic systems are vitally important to our province’s economic and ecological health.

Found at the mouth of a river, estuaries can also include entire “drowned river valleys”. A river ‘drowns’ when local or global sea level rise occurs and salt-water is able to move upstream. Estuary ecosystems receive nutrients and oxygen both from the freshwater of the river and the tidal influx. This unique mixing ground is able to support large and diverse populations of marine shellfish, fish, birds and plants. “Nurseries of the sea,” estuaries provide habitat for the young of many creatures. Economically important species, including eels, smelt, salmon, oysters, mussels and soft shelled clams all benefit from the nutrient-rich waters that make up Nova Scotia’s estuaries. They can also become popular feeding grounds for migratory birds like the Canada goose. Other notable birds that hunt in estuaries include ospreys, herons and bald eagles.

A wide variety of plant species have also evolved to grow in the brackish environment. Indeed, an estuary can produce twice as much plant material per hectare as an agricultural field. Estuarine vegetation such as eelgrass can filters herbicides, pesticides, heavy metals, excess sediments and nutrients from the water that comes from the river’s watershed.

Filtration prevents contaminants from entering the estuary. This filtering is a significant service to Nova Scotia’s economy. After all, many commercial species can be found in estuaries. For example, the Annapolis Basin soft-shell clam industry provided $2.3 million in revenues in 2006.

Other goods and services provided by these important parts of the watershed include wildlife habitat, water supply, erosion, wind, wave barrier, storm and flood control and recreation. Overall, studies place the value of each hectare of an estuary between $5,792 - $ 24,330 per year.

Although not always the result of human action, excess nitrogen presents a serious threat to the health of our estuaries. When too much nitrogen enters the marine environment, algal populations can explode. These algae can cause red tide or thick mats, which can smother other life. Some algae also produce toxins that can affect organisms across the entire estuarine food web.

Poorly treated sewage and agricultural runoff are two major sources of excess nitrogen. We can protect the health of our local estuaries by ensuring that these contaminants stay out of the watershed. Being good stewards of our estuaries can simply mean making sure that our personal septic systems are functioning properly and pumped regularly. As well, when waterways farm or woodlot, we can make sure that vegetative buffers are planted along the banks.

NICOLE OLIVER is the Community Engagement Coordinator at the Clean Annapolis River Project (CARP). Coastlines is a project of the Ecology Action Centre, appearing in community papers around the province as well as at www.ecologyaction.ca/coastlines. Coastlines is supported by the Nova Scotia Habitat Conservation Fund with contributions from hunters and trappers.