Abstract
To enhance the conditions for producing shellfish in coastal waters, the possibility of employing artificial upwelling of nutrients is explored. The effectiveness of a submerged discharge of fresh water is studied by means of a numerical buoyant plume model, BJET, and laboratory simulations. An optimisation of the entrainment of deeper, nutrient-rich water to the proper intrusion depth is demonstrated. The studies show that a downward directed jet of fresh water below the euphotic zone can lift significant amounts of nutrients to the primary production near the surface. The outlet must be large enough to lift the deeper water through the pycnocline to the desired depth of primary production. The results are applied to a possible discharge arrangement in the Samnangerfjord, to the east of Bergen, Norway, using field data from 1999. With a discharge of up to 8 m3/s of fresh water at 35 m depth, the entrainment of deeper water into the buoyant plume, up to the 15 m depth, is 12 to 13 times as much. The chosen arrangement could give an expected vertical transport to the euphotic zone of 467 kg d−1 N, 46 kg d−1 P and 555 kg d−1 Si during the summer growth period. This includes periods of coastal downwelling with greatly reduced values of nutrients, but not periods of strong, deep stratification with deeper intrusions. Further optimisation is possible using active controls of the discharge system.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call