Macrobenthic Community And Its Environmental Factors In Tianjin Coastal Area,China

Macrobenthos is a most complex group in marine ecology and it plays an important role in substance circulation,energy flow and marine environmental monitoring.Based on the macrobenthic data,sea water and sediments environmental factors in spring and summer of 2017,summer of 2018 and autumn of 2019 from Tianjin costal area in Bohai Bay.The changes of community structure and diversity of macrobenthos were analyzed meanwhile the status and distribution of pollutants in the water and sediments environments were also analyzed.The correlations among macrobenthic community structure,diversity and environmental factors were studied by multivariate analysis methods.The results were as follow:(1)The results showed that 27 species of macrobenthos were identified in spring of 2017,Musculus senhousei was the absolutely dominant specie,and the average abundance of macrobenthos was 44 ind./m2,the average biomass was 4.53 g/m2.Meanwhile,there was 40 species of macrobenthos in summer of 2017 and the absolutely dominant specie was also Musculus senhousei,and the average abundance of macrobenthos was 112 ind./m2,the average biomass was 98.53 g/m2.There were 41 species of macrobenthos in summer of 2018,and Potamocorbula laevis were absolutely dominant species,and the average abundance of macrobenthos was 44410 ind./m2 and the average biomass was 224.57 g/m2.And 52 species of macrobenthos were identified in autumn of 2019,the average abundance of macrobenthos was 116 ind./m2 and the average biomass was 51.78 g/m2,Ringicula doliaris and Nassarius succinctus were absolutely dominant species.Showed the seasonal change trend of summer>autumn>spring.The diversity index of macrobenthos d,J,H' in each voyage has no obvious changes law in general,summer and autumn>spring.The macrobenthos of Tianjin costal area can be divided into 3 groups at the similarity level of 5%in the spring of 2017;and divided into 7 groups at the 25%similarity level in the summer of 2017;and divided into 8 groups at the 27%similarity level is divided into 8 groups;divided into 7 groups at the 34%similarity level in autumn of 2019.There was a large difference in the division of each group in each year,and the overall similarity coefficient among each groups was very low.(2)In spring of 2017,the water depth was 2.7?18.4 m,the water temperature was 10.3?16.2?,the salinity was 30.1?31.4,and the chlorophyll-a content was 1.05?21.80?g/L.In summer of 2017,the water depth was 3.0?23.0 m,the water temperature was 24.3?28.3?,the salinity was 31.2?32.7,and the chlorophyll-a content was 1.63?12.63?g/L.In the summer of 2018,the water depth was 2.5-21.0 m,the water temperature was 25.6?29.3?,the salinity was 27.0?30.1,the chlorophyll-a content was 0.48?7.18?g/L,the total organic carbon content was 0.49?0.93%,the sulfide was 45.09?144.67 ?g/g,the total nitrogen content was 647.22?1317.89?g/g,and the total phosphorus content was 84.00?696.64?g/g,with the range of median particle size was 6.76?18.86 ?m,the sedimentary type was silty.In autumn of 2019,the water depth was 3.6?13.3 m,water temperature was 2.0?4.6?,bottom salinity was 29.8?31.6,chlorophyll-a content was 1.49?33.62?g/L,the total organic carbon content was 0.50-1.00%,sulfide content was 13.13?172.42 ?g/g,total nitrogen content was 737.64?1308.34 ?g/g,total phosphorus content 103.75?538.54?g/g,the median particle size of sediments was 7.21?25.33?m and the sediments type was clay silt.(3)The BIOENV analysis test between Tianjin costal areas macrobenthos data and related environmental factors showed that in spring 2017,the best combination of environmental factors was water temperature and chlorophyll-a.In summer 2017,the best combination of environmental factors was single factor water temperature.In summer of 2018,the best combination of environmental factors was the water depth,water temperature,chlorophyll-a,sulfide,and median particle size.In autumn 2019,the best combination of environmental factors was water depth,salinity,sulfide,and median size.Pearson correlation analysis showed that in spring 2017,the habitat density and water temperature were significantly positively correlated;in summer 2017,the species richness index and water temperature were significantly positively correlated;In the summer 2019 habitat density and water temperature were significantly positively correlated,the benthic biomass and salinity were significantly positively correlated,and the diversity index and salinity were significantly negatively correlated.CCA and RDA analysis showed that water depth,temperature,sediment nutrients and sediments particle size were the main environmental factors that affected the macrobenthos distribution.