| According to the investigations of macrobenthos in Jiaozhou Bay in July 2015,January 2016,April 2016 and November 2016,the macrobenthos species composition,dominant species,abundance,biomass,biodiversities and community structure were studyed combined with many environmental factors.Environmental quality of Jiaozhou Bay was evaluated by index of diversity.Correlation between environmental factors and community structure were studied via BIOENV analysis,and ariation of ecological parameters of macrobenthos in Jiaozhou Bay were analyzed by comparing with historial studies.The main results were as follows:There were 112 species identified in four seasons in Jiaozhou Bay,and the dominant species of the year were Heteromastus filiformis,Nemertinea and Nephtys oligobranchia;53 species were identified in summer,and the dominant species were: Pista sp.,Paralacydonia paradoxa,Nephtys oligobranchia,Sternaspis scutata and Eriopisella sechellensis;47 species were identified in spring,and the dominant species were: Glycera onomichiensis,Lumbrineriiae,Heteromastus filiformis,Protankyra bidentata,Xenophthalmus pinnotheroides and Ruditapes philippinarum;44 species were identified in autumn,and the dominant species were: Lumbrineriiae,Nemertinea,Goniada maculate and Raphidopus ciliatus;66 species were identified in winter,and the dominant species were: Nephtys oligobranchia,Lumbrineriiae and Brachiostoma belcheri tsingtauense.Heteromastus filiformis is the most dominant specie in spring,autumn and winter.The mean abundance of the year was 167.60 ind./m2;the mean abundance in summer was 201 ind./m2,and the horizontal distribution of abundance showed the tendency increased gradually from west to east;the mean abundance in spring was 171 ind./m2,and the horizontal distribution of abundance showed the abundane inside Jiaozhou Bay was higher than outside the bay in general;the mean abundance in autumn was 120.91 ind./m2,the horizontal distribution of abundance showed the trend that abundance decreased from the area inside the bay to the area outside the bay;the IV mean abundance in winter was 177.50 ind./m2,the horizontal distribution of abundance showed the abundance in nearshore area inside Jiaozhou Bay was highest,followed by the area outside the bay and then offshore area inside Jiaozhou Bay.The mean biomass of the year was 257.5 ind./m2;the mean biomass in summer was 22.3 ind./m2,the horizontal distribution of biomass was irregular and the domiant group was polychaete;the mean biomass in spring was 495.4 g/m2,there were vast Ruditapes philippinarum,and the horizontal distribution of biomass showed an increasing trend of abundance inside Jiaozhou Bay to outside Jiaozhou Bay;the mean biomass in autumn was 117.8g/m2,and the horizontal distribution of biomass showed the same trend as in spring;the mean biomass in winter was 159.5 g/m2,and abundance inside Jiaozhou Bay was higher than outside the bay in general.The average value of Shannon-Wiener index(H')of macrobenthos in the investigated area of the year was 2.57,the average value of Margalef's richness index(d)of the year was 0.88;the average value of Pielou's evenness index(J)of the year was 1.41;In summer,the value range of H' was 1.68-3.48,with an average value of 2.79,the value range of d was 0.69-0.97,with an average value of 0.88;the value range of J was 0.76-2.25,with an average value of 1.60;In spring,the value range of H' of macrobenthos in the investigated area was 1-3.00,with an average value of 2.28,the value range of d was 0.52-1.00,with an average value of 0.88;the value range of J was 0.33-2.11,with an average value of 1.27;In autumn,the value range of H' of macrobenthos in the investigated area was 1.55-3.08,with an average value of 2.50,the value range of d was 0.76-1.00,with an average value of 0.88;the value range of J was 0.67-2.21,with an average value of 1.19;In winter,the value range of H' of macrobenthos in the investigated area was 1.19-3.54,with an average value of 2.65;the value range of d was 0.91-2.29,with an average value of 1.47;the value range of J was 0.46-1.00,with an average value of 0.87.The results showed that the seasonal biodiversity of macrobenthos is obvious.According to the result of CLUSTER,there was a slight difference of community structure in four seasons,macrobenthos could be divided into two groups in summer(S3,S4 and S8 for Group I;S1,S2,S5,S6,S7,S9,S10,S12,S13 and S14 for Group?);macrobenthos could be divided into two groups in spring(S1,S2,S3,S5,S6 and S8 Group I;S4,S7 and S10 for Group?);macrobenthos could be divided into two groups in autumn(S1,S2,S3,S4,S5,S6,S10,S11 and S12 for Group I;S7 for Group?);macrobenthos could be divided into three groups in winter(S7 and S10 for Group I;S1,S2,S3,S4,S6,S8,S11 and S12 for Group?;S9 for Group?).According to the correlation analysis between abundance matrix and environmental factors,the best combination that affected the community structure of macrobenthos in spring most was depth+ temperature+ chlorophyll a +median diameter(r= 0.936);the best combination that affected the community structure of macrobenthos in autumn most was depth+ salinity + chlorophyll a +median diameter,(r=0.909);the best combination in winter was depth+ p H+median diameter,(r=0.424).According to the comparion between the historical data of macrobenthos in Jiaozhou Bay and this study,we found both the number of total species and average abundance decreased year by year.The dominant position of Raeta pulchella(dominant species in the 80s)had faded away,and dominance of Raphidopus ciliatus also decreased gradually in recent years.Some species feed on sediment,such as Lumbrineriiae,became new dominant species.The proportion of average abundance of Molluscs dropped significantly,but average abundance of Echinoderm showed no obvious difference.The partition of community structure on macrobenthos changed a lot in the past(macrobenthos could be divided into six groups in 80 s,five groups in 90 s and three or four groups now),showed a simplifying trend and partial succession.According to the comparion between this study and similar studies of other survey area,the number of species were fewer,average abundance was in the medium range and average biomass was higher on macrobenthos in Jiaozhou Bay. |
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