The same mussels as might be served on a plate in white wine could also help clean excess nitrogen and algae from fjords, thereby preventing oxygen deficiency – hypoxia.
Researchers studied 1,100 tonnes of mussels from an 18 hectare area of Skive Fjord. They found that the tasty creatures reduce oxygen deficiency because they eat algae that is there in part because of nitrogen emissions from agriculture.
"It surprised me that the mussels were so effective at removing nitrogen in Skive Fjord,” said Jens Kjerulf Petersen, a professor at the Danish Shellfish Centre at the Technical University of Denmark (DTU) to the scientific newspaper Videnskab. "If we can subsequently sell the mussels, that would lower the price of the solution significantly.”
The project was designed to measure the effectiveness of mussels at removing pollutants. Researchers were surprised at how well they did.
Karen Timmermann, a senior fellow at the Institute of Bioscience at Aarhus University described the experiment.
"In Skive Fjord we had 18 hectares of mussel farm that cleaned out and improved the clarity of the water in an area ten times as large,” she told Videnskab.
The circle of nitrogen
Researchers behind the project believe that farmers can benefit from the mussels.
“These ‘environmental mussels’, as we call them, contain a number of valuable proteins suitable for livestock so we would not need to import as much soy or protein from other sources,” said Kjerulf.
Harvesting the mussels and reusing them as fertiliser removes nitrogen from the water and puts it back in the land where it is needed.
“It closes a portion of the nitrogen cycle,” said Timmermann.
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The mussels are not a standalone solution, but researchers agree that the mussels can be of help in getting rid of the dangerous amounts of nitrogen in coastal waters.
“Nitrogen from manure ends up in the sea, groundwater and streams from decades of overuse of fertilisers in Danish agriculture, the mussels could help remove it,” said Kjerulf.