Abstract
Air was introduced into a stream of water using a porous cylindrical sparging element placed inside a hose, producing a large number of tiny microbubbles (d ~ 1mm) and mixing them with the water flow inside the hose. Eight such bubble producers were fixed in parallel 50 cm apart. Each bubble producer was attached to a hose 1"" in diameter and 6 m long. These hoses were provided with 6 mm holes 10 cm apart and with an angle of 120° between them in the transversal plane. The resulting grid of hoses, which covered an area of approximately 21 m2, was built to spread the mixture of bubbles and water in a continuous horizontal 'bubble carpet'. The bubble producer system was towed behind the R/V Jan Mayen (at depths of 10, 15 and 25 m) from which air- and water flow was regulated. The vertical distribution of Calanus was recorded before and after a given area was bubbled, using an array of net samplers. The results clearly showed that the vertical distribution of Calanus changed after a given area was bubbled, i.e. large quantities of Calanus were lifted towards the surface by the bubble plume and associated upwelling flow.
