Effect Of The Ballast Water Treatment System On Survival Of Natural Zooplankton Communities Onboard The Vessel Nase More

The introduction of non indigenous species has been recognised as a serious threat to global biodiversity. Several vectors of the introduction in marine ecosystems are known; the most significant being aquaculture activities and shipping, i.e. hull fouling and ballast water. This paper describes testing of the ballast water treatment system on board vessel Nase more in Sibenik bay and Omisalj bay. The effect of cyclonic separation in hydrocyclones followed by ultraviolet radiation in the UV reactor on the survival of zooplankton organisms was examined. Sea water was pumped through the hydrocyclone cluster separately, and in combination with UV radiation in 3 consecutive cycles. Almost identical results were obtained in treatments with and without UV radiation, which indicates satisfying effectiveness of mechanical treatment in hydrocyclone for zooplanktonic organisms. Control samples from surrounding area, samples separated by hydrocyclone as well as those that have passed through the treatment system in the tanks on board, representing the ballast water tanks, were collected and analysed. By comparing the samples from surrounding aquatoria and samples collected in the tanks onboard it was concluded that 62.7% to 54.5% of the organisms was separated by the hydrocyclones, meaning that 37.3% to 45.5% of the organisms passed through the system and was collected in the tanks onboard, from which 4.7% to 32.8% were alive. After 8 hours average share of live individuals was 14.9%, and after 24 hours only 1.8% from the total number of organisms in the surrounding sea. Experiments demonstrated the successful use of the ballast water treatment system for inactivation of zooplankton organisms in seawater.