Can shellfish aquaculture save coastal bays?

A recent study has confirmed that mussel and oyster farming can play a key role in improving water quality by removing hundreds of tonnes of nitrogen from coastal bays and estuaries.

A meta-analysis published in Aquaculture Reports reveals that mussel and oyster farming is likely to remove nearly 334 tonnes of nitrogen per year from Atlantic Canada’s nearshore ecosystems – representing a major step in bioremediation efforts. The study also found that suspended mussel aquaculture removed more environmental nitrogen per hectare of farm area than suspended or ground-based oyster aquaculture. Based on these factors, the researchers concluded that growing and harvesting shellfish, especially mussels, has a restorative effect on nearshore ecosystems.

In Atlantic provinces like New Brunswick (NB) and Prince Edward Island (PEI), nutrient run-off from agriculture has damaged coastal and estuarine ecosystems. The increased nitrogen concentration in the water contributes to eutrophication – the enrichment of water by nutrient salts. This process negatively impacts water quality and contributes to toxic algal blooms and dead zones in the water.

Shellfish aquaculture has been trialled as a method to mitigate eutrophication. Since bivalves are filter-feeders, they can potentially extract excess nutrients form the water. They’re also able to incorporate phytoplankton and carbon into their tissues as they mature before harvest. For nitrogen specifically, bivalves can remove it from the surrounding water by absorbing it in their shells and burying it in sediments. Other case studies have suggested that oyster and mussel aquaculture have the same denitrification potential as wild oyster and mussel beds. These studies also indicate that bivalve aquaculture provides major ecosystem benefits. Oysters and mussels enhance the bottom habitat of coastal areas and can stimulate sediment creation, nutrient cycling and carbon sequestration.

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