The Effect Of Mariculture On Zooplankton Community Structure And Distribution Of Their Resting Eggs

The physicochemical parameters and zooplankton community structure were investigated in the different marine ecological types in Shenao Bay,Nanao Island,Shantou City from January to June 2016.The distribution,potential recruitment and hatching success of zooplankton resting eggs in the sediments,and deposition flux of resting eggs were studied as well as epiphytic zooplankton community strycture in the surface of seaweeds（Gracilaria lemaneaformis and Gracilaria chouae）.The main results were included as following:1.During the investigation,46 species of zooplankton,including 27 species of copepods,2 cladocerans,6 protozoan,1 rotifer and several planktonic larvaes were identified in Shenao Bay.The dominant species of zooplankton were Paracalanus parvus,Oithona similis,Microsetella norvegica,Euterpinan acutifrons,Cirripedia and Favella campanula.The zooplankton abundance ranged from 3 to 399 ind.·L^-1,which were higher in summer and spring than that in winter.Zooplankton were more abundance in abalone cultivation area than others.Redundancy analysis（RDA）showed that water temperature,salinity,active phosphate,dissolved oxygen and total phosphorus were the significant factors.2.Size-frequency distributions of zooplankton indicated that mariculture made a big influence on zooplankton body size.The body size of zooplankton ranged from 0.06 to 1.7 mm and most of them were under 1 mm with fluctuating significantly.There was a significant difference among different mariculture areas.3.In Shenao Bay,the potential recruitment of zooplankton resting eggs ranged from 4.67 x 10⁵ to 16.67 x 10⁵ ind.·m^-3,and the abundance of resting eggs ranged from 6.67 x 10⁵¹8.67 x 10⁵ eggs·m^-3,with the hatching rate ranged from 58.89% to 91.67%,and averaged 74.61%.The low potential recruitment and abundance of zooplankton resting eggs were recorded in fish cultivation area,and high potential recruitment and hatching rate of resting eggs were in G.lemaneiformis cultivation area and abalone-G.lemaneiformis cultivation area.Pearson correlation analysis showed a negative correlation between the potential recruitment of zooplankton resting eggs in the sediment and zooplankton abundance in the water,especially in G.lemaneiformis cultivation area and abalone-G.lemaneiformis cultivation area（P<0.05）,which indicated that planktonic copepods and resting eggs bank were in dynamic complementary,and population were in a relatively stable status.4.The deposition flux of zooplankton resting eggs ranged from 118¹92 ind.·m^-2·d^-1 with eaveraged 153 ind.·m^-2·d^-1.There wre significant differences in different cultivation areas.Lowest deposition flux of zooplankton resting eggs was recorded in abalone cultivation area.After G.lemaneiformis harvest,the abundance of zooplankton resting eggs increased lightly in G.lemaneiformis cultivation area and abalone-G.lemaneiformis cultivation area,however,potential recruitment was decreased.5.There were 8 species of epiphytic zooplankton in surface of G.lemaneaformis and G.chouae,including 3 copepods,which belonged to Harpacticoida,and several planktonic larvae.Copepods were the preponderance taxa.The abundance of epiphytic zooplankton was much higher than planktonic zooplankton in water.Seaweeds provided habitat for epiphytic zooplankton,which could enrich zooplankton.