Hopp til hovedteksten
Mussel
Photo: Øivind Strand
Print friendly version

Deepwater supply to the algae

Scientists from the Institute of Marine Research use simple technology in the Lysefjord large scale fjord-laboratory to study how supply of nutrient-rich deeper water to the upper water layers increase micro-algae production during the summer season. New results demonstrate how this increase is converted to mussel growth. 

- The mussel often need long time to restore after spawning in late spring, and meat content are therefore typically low during summer. By bringing up some of the nutrients stored in the fjord basin water we see large possibilities in developing efficient and sustainable aquaculture, primarily exemplified by production of high quality mussels, says Tore Strohmeier who is one of the researcher working at the fjord laboratory.      

By assisting nature to maintain the production of algae during the summer period our results showed that the mussels restore and enhance their meat content within two weeks after spawning. Mussels have no market value after spawning and a fast recover is essential in mussel farming. In general the mussels grown in the area influenced by upwelled deeper water also show higher meat yield than mussels from the outside area. Typically, mussels grown in fjords rarely show high meat content in summer.

Simple and sustainable technology

 

The technology used at the fjord laboratory is environmental friendly and based on classical hydro-engineering.

- Fresh water from the outlet of a hydropower plant is brought down to a depth of 34 meters by a pipe. This water is mixed with the nutrient rich deeper water and supply nutrients to maintain the algae production in the upper layers, says researcher Øivind Strand.

A one meter drop of the freshwater collected from the hydropower plant supports enough energy to push out the water in the deep. While mixing the deeper marine water it ascends by buoyancy up to the layers of similar density, under the brackish surface layer. This will typically be at 5-8 meter, where light conditions can support high algae production.

A natural process

- The algae spring bloom that occurs every year is initiated when light and nutrients can support production increase. After some weeks nutrients are depleted and the blooms vanish. New supply of nutrients from the freshwater runoff or from deeper water may give short periods of new blooms during the summer, but the upwelling by using simple technology in the Lysefjord fjord-laboratory will provide a controlled and stable algae production which also can efficiently be converted to high quality seafood by mussel farming.

Facts: Forced upwelling of nutrient rich deepwater

  • Deepwater has a naturally balanced composition of nutrients
  • Forced upwelling of deep water lift nutrients up and into the light so the nutrients can be utilized by the phytoplankton
  • In the area of influence the production of phytoplankton and suspension feeders (e.g. blue mussel) can be tripled
  • Increased phytoplankton production bind the greenhouse gas CO2
Sustainment from the controlled upwelling of nutrient rich deepwater

Contact

Øivind Strand
473 08 955
Tore Strohmeier
907 20 754
Jan Aure
913 22 983
Beate Hoddevik
908 21 630