Study On The Plankton And Its Invasive Mechanism In The Ballast Water Of Exotic Ships Entering Fujian

Cargo vessel ballast water has been one of the most important ways for the spread of harmful organisms all over the world.Ballast water samples were collected and analyzed from 13 international ships which docked at 4 major ports in Fujian during 2006-2008.6 ballast water samples were cultured,in order to observe the viability of the plankton,and the relationship between the plankton and temperature,salinity and other factors.The interspecific competition between Woloszynskia sp.and Skeletonema costatum was studied simulating the condition when the plankton in the ballast water was discharged into the destination port.The mechanism of biological invasion was further discussed by microalgae via ballast water.Main results were showed as follow:1.In the 13 samples examined,a total of 239 taxa belonged to 86 genera in 7 phytoplankton phyla were identified:174 taxa in 50 genera belonged to Bacillariophyta,36 taxa in 19 genera belonged to Chlorophyta,19 taxa in 9 genera belonged to Pyrrophyta,6 taxa in 5 genera belonged to Cyanophyta,2 taxa in 1 genera belonged to Xanthophyta,1 taxa belonged to Chrysophyta and Euglenophyta respectively.The higher frequent species were Cyclotella striata,Thalassionema nitzschioides,Thalassiosira spp.,Pleurosigma spp.,Actynoptychus undulates and Ditylum brightwellii.A total of 60 red-tide causative algae were found,46 taxa belonging to Bacillariophyta,11 taxa belonging to Pyrrophyta,2 taxa belonging to Cyanophyta and 1 taxa belonging to Chrysophyta.There were significant difference in density in 13 international ships,ranging from 0 to 3×10~4 cells/L.2.A total of 52 taxa(including planktonic larva) belonged to 30 genera in 5 zooplankton phyla were identified.Arthropoda were dominant phyla,with 44 taxa in terms of number of taxa encountered.39 taxa(including 10 taxa of larva) belonging to copepoda were identified,with 26 taxa in Calanoida,11 taxa in Cyclopoida and 2 taxa in Harpacticoida.The density ranged from 0 to 4.24 ind/L.3.The relationship between plankton abundance and the type of the ship, ballast water salinity and ballast water age:the ballast water age was usually short (less than 5 days) in Bulk carrier for short route.And the plankton abundance in Bulk carrier was higher than that in Container ship:The plankton abundance decreased with increasing ballast water age,the effect of ballast water age on plankton abundance was significantly;The plankton abundance was influenced by ballast water salinity,we can identify the ballast water source according to the salinity of ballast water:fresh water(＜10‰);marine-estuarine water(10-31‰); marine water(＞31‰).4.Phytoplankton of the ballast water were cultured with f/2 culture medium,a total of 13 diatoms and 1 dinoflagellate were cultured.Thalassiosira spp.was the highest frequency of occurrence in cultured.Skeletonema spp.,Nitzschia spp and Chaetoceros spp.were also common.5.The effects of phosphate concentrations and initial cells density on population growth and interspecific competition between Woloszynskia sp.and Skeletonema costatum were investigated,the result showed that:The growth rate of both algal increased as the phosphate concentration increased during uni- and bispecific cultures,Woloszynskia sp.and Skeletonema costatum interfere the growth each other;there were density dependent and resource utilization competition in the bispecific culture.