Nygaard, K. K. NIVA, kari.nygaard@niva.no
Vedal, J. K. University of Oslo,
Bjerkeng, B. B. Niva,
Johnsen, T. T. NIVA,
LÝmsland, E. E. NIVA,

 
LIFE AND DEATH IN A WATER JET - ECOSYSTEM CONSIDERATIONS.
 
Experimental investigations aiming to answer possible effects of water jet on pelagic organisms were performed during the period 5 to 8 of August 1997. The experimental results were then combined with literature data and extrapolated on the basis of the total number of water jet units and total quantities of processed water in specified reference volumes. The effects are described and analysed on seasonal and annual bases and with consideration of local effects in areas with frequent HSC traffic. All water samples for analyses of possible effects of water-jet processing were taken on board the high speed vessel. Three different sources of water were sampled on board the ship, representing untreated water, water that had passed the water jet unit and a sample of water pumped through the cooling system. Results from water samples after passing a water jet propulsion indicated some reduction in algal number without any clear reduction in algal production for the remaining algae. No significant difference in numbers of dead or damaged zooplankton were found in these samples compared to the reference samples. However, the type of damages observed for the zooplankton in these samples may indicate a possible loss of 20 percent. The environmental impact of traffic by high speed craft in a specific region will be a function of total volumes processed, compared to relevant total volumes or renewal of the water bodies in question. When combining the effect on organisms passing the system with the actual volume that passes the jet propulsions, the effect will be at least several orders of magnitude lower than normal ecological loss processes such as death by predation.
 
Day: Friday, Feb. 5
Time: 12:00 - 12:15pm
Location: Hilton of Santa Fe
 
Code: SS11FR1200H