Changes In Water Quality And Its Impact On The Growth In Scallop Culture Area Of Yantai

In order to understand the impact of seawater quality and phytoplankton community structure in scallop culture areas of Yantai.In our study,11 scallop culture areas in Laizhou Bay and Sishili Bay were tested for water quality,phytoplankton were classified and counted.Scallop breeding density,yield and income were investigated in the middle of each month from May to November 2018 and 2019.Our study hopes to provide some basis for scallop breeding.In our study,environmental factors such as temperature,pH,salinity,dissolved oxygen,chemical oxygen demand,total phosphorus,active phosphorus,and inorganic nitrogen were detected,vibrio and heterotrophic bacteria were cultured and counted in seawater,and phytoplankton were classified and Counted.Using nutrition index(E)to evaluate seawater nutrition state,Nemerow index method(P)and single factor pollution index method(P_i)to evaluate seawater quality,Shannon-Winner index(H'),Pielou index(J)and Margalef index(D)calculate the diversity,uniformity and richness of phytoplankton species and evaluate the water quality of scallop culture area.Spss19.0 was used to analyze the correlation between phytoplankton and environmental factors,environmental factors and environmental factors.Canoco5.0was used to analyze the correlation between environmental factors and phytoplankton community structure.Studies have shown that in 2018 and 2019,the seawater temperature were11.06~27.26?and 9.08~27.46?in Yantai scallop culturre areas;The average pH were 8.14 and 8.11 in Laizhou Bay,and the average pH were 8.10 and 8.09 in Sishili Bay;The average salinity were 31.19‰and 30.42‰of Laizhou Bay,and the average salinity were 31.29‰and 31.34‰of Sishili Bay;The average dissolved oxygen were 7.49 mg/L and 7.32 mg/L of Laizhou Bay,and the average dissolved oxygen were 7.77 mg/L and 7.60 mg/L in Sishili Bay,respectively;The average COD were 1.29 mg/L and 2.00 mg/L of Laizhou Bay,and the average COD were 1.51 mg/L and 1.57 mg/L of Sishili Bay,respectively.Except for exceeding the national Class II water quality standards in individual months and individual culture areas,the rest were within the standard range.The variation range of inorganic phosphorus,total phosphorus and inorganic nitrogen were 0.0004~0.018 mg/L,0.0018~0.0375 mg/L and 0.0714~0.5018 mg/L in Yantai sea area(including Laizhou Bay and Shishili Bay)of 2018,and were 0.0004~0.0533 mg/L,0.0098~0.1088 mg/L and 0.0239~0.4338mg/L in 2019.Individual culture areas exceeded the country in May,June,October and November Class?water quality standards,the rest were within the standard range.The average values of N/P were 83.46 and 32.77 in 2018 and 2019.The results show that the Yantai scallop culture area was in a phosphorus-restricted state.The variation range of Vibrio and heterotrophic bacteria were 0.5~6100 cfu/ml and 1~12350 cfu/ml in Yantai sea area(including Laizhou Bay and Shishili Bay)of 2018,were 1.2~6950 cfu/ml and 6.5~4300 cfu/`ml in 2019.A total of 89 species belonging to 50 genera of 5 phylum phytoplankton were found in 2018,including 62 species belonging to 33 genera of diatom,15 species of 9genera of Prorophyta.A total of 81 species belonging to 48 genera of 5 phylum phytoplankton were found in 2019,including 57 species belonging to 29 genera of diatom,10 species of 7 genera of Prorophyta.In 2018 and 2019,the diatom phytoplankton accounted for the absolute advantage in the phytoplankton community structure in the Yantai Scallop culture area.The density of phytoplankton in the sea area of Yantai scallop farming varied from 0.16 to 148.68×104 cell/L in 2018,and the density of phytoplankton varied from 0.45 to 67.56×104 cell/L in 2019.The dominant species of phytoplankton were 20 and 17 in 2018 and 2019,most of which were diatoms.The results of phytoplankton biodiversity analysis indicate that the phytoplankton community structure in Yantai Scallop culture area is stable and the seawater quality is favorable.The seawater nutrition index(E)ranged from 0.013 to 2.15 in scallop culture areas of Yantai in 2018,and was 0.014 to 6.61 in 2019.The results show that the scallop culture area were basically in a state of poor nutrition except for a few months in 2018.The nutritional level of seawater in 2019 is higher than that in 2018.The Nemerow index(H')ranged from 0.013 to 2.15 in scallop culture areas of Yantai in2018,and was 0.014 to 6.61 in 2019.The results of environmental quality assessment indicate that the scallop culture areas in Laizhou Bay and Shilili Bay were in clean and relatively clean state except for a few months.On the whole,Yantai scallop culture area(including Laizhou Bay and Shishili Bay)are more suitable for scallop farming.Spass correlation results showed that the density of phytoplankton was positively correlated with dissolved oxygen and inorganic phosphorus in Yantai scallop culture areas of 2018 and 2019;The results of canonical correspondence analysis showed that temperature,dissolved oxygen and nitrogen and phosphorus nutrients were the main factors affecting the distribution of phytoplankton communities.The difference in scallop farming density is mainly reflected in the raft spacing,cage spacing and the number of scallops stocked in each cage.The difference in scallop farming benefits is mainly reflected in the size of the scallop shell column.According to the number of surface cultured scallop cages per unit area,the breeding density from high to low was S2>S1>L4>L1>L7>L6>L2>L8 in different scallop culture areas in 2018,and was S2>S1>L4>L1>L7>L2>L8>L6 in 2019.According to the size of scallops,the breeding income was S1>L7>S2>L2>L6>L8>L1>L4 in order of different scallop culture areas in 2018,and was S1>S2,L7and L8>L1>L6 and L2>L4 in order of 2019.The results show that in a certain sea area,the breeding density is inversely proportional to the breeding income,and the phytoplankton density is directly proportional to the breeding income.During the breeding process,monitor the density of phytoplankton in culture areas,so as to adjust the breeding density and the sea area in time,and ensure the sustainable development of scallop culture in Yantai sea area.