| This article discusses the relationship of community structure,secondary productivity,feeding functional group changes of the macrobenthos and the environmental impact factors,based on the analysis of biological samples,water parameters and physicochemical factors of deposition of macrobenthos in Daya Bay from January to December,2016.(1)361 species of macrobenthos were identified,which include: Polychaeta(141),Mollusca(97),Crustacea(76),Echinodermata(16)and other phylum(31);seasonal variation of species number is Spring(214)> Winter(147)> Summer(133)> autumn(107).The average density is 800 ind/m2,and the one of Mollusca(577 ind/m2)and Polychaeta(184 ind/m2)are high;the monthly variation of average density in March is the highest(1747 ind/m2),the one in July is lowest(309 ind/m2),the seasonal variation of average densities is Spring(1153 ind/m2)> Autumn(754 ind/m2)> Winter(608 ind/m2)> Summer(374 ind/m2).The average total biomass is 86.88 g/m2,the one of Molluscais the highest(76.00 g/m2),the monthly variation of average total biomass in April is the highest(186.89 g/m2),and the one in September is lowest(27.57 g/m2).The seasonal variations of average biomass is Spring(134.40 g/m2)> Winter(92.34 g/m2)> Summer(71.35 g/m2)> Autumn(68.4 g/m2).The monthly variation and seasonal variation are mainly affected by Mollusca Timoclea scabra.(2)The anniversary analysis community cluster of the Daya Bay community structure is divided into three groups,and the seasonal analysis of community cluster can be divided into 4 groups,the analysis of community stability(ABC Curve)shows that the macrobenthos in Daya Bay is unstable.(3)From 1984 to 2016,the major constructing groups of macrobenthos in Daya Bay gradually change into Polychaeta and Mollusca from Mollusca and Crustacea,the proportion of Polychaeta is gradually increasing,and the proportion of Mollusca and Crustacea have been declining.The dominant species of macrobenthos in Daya Bay gradually evolve into the simple dominant species of Timoclea scabra and Turritella bacillum from multiple species,and the single dominant species of Timoclea scabra is in a significant stronger position.(4)The annual average of secondary productivity of macrobenthos in Daya Bay is 10.14 g AFDW·m-2·a-1,the annual average of P/B value is 0.65 a-1.The monthly variation value of secondary productivity between 2.72~22.24 g AFDW·m-2·a-1,The seasonal variations of secondary productivity are Spring(15.79 g AFDW·m-2·a-1)> Winter(10.52 g AFDW·m-2·a-1)> Autumn(7.01 g AFDW·m-2·a-1)> Summer(5.86 g AFDW·m-2·a-1).The monthly and seasonal analysis of secondary productivity shows that the Mollusca and Polychaeta contribute the most among various biological groups,and the Phytophagous group(Pl)contribute the most among feeding functional group.Comparing with other sea areas,the secondary productivity level in Daya Bay is higher than the Bays like Bohai Bay,Sanduao,Sanggou Bay and Caizhou Bay etc.,lower than the Jiaozhou Bays and Ruzhou Bay,and it is similar to the secondary productivity result of Daya Bay in 2004,higher than the one in 1988,lower than 2013.(5)The macrobenthos were categorized into five functional groups based on feeding types including the Detritivorous group(De),the Camivorous group(Ca),the Omnivorous group(Om),the phytophagous group(Ph)and the Planktophagous group(Pl)in the Daya Bay.The annual analysis on feeding functional group of macrobenthos in Daya Bay shows that the De(99),Ca(95)and Pl(69)are the dominant functional group.The Pl(530 ind/m2)is the highest in the monthly average densities of feeding functional group,the Ca(114 ind/m2)takes the second place.The Pl(73.72 g/m2)is the highest in average biomass,and the De(6.74 g/m2)takes the second place.The major dominant functional groups of seasonal feeding functional group are Ca(103),De(93)and Pl(73).The seasonal average densities are Pl(413 ind/m2)> Ca(169 ind/m2)> De(124 ind/m2)> Om(17 ind/m2)> Ph(1 ind/m2);the average biomasses are Pl(78.22 g/m2)> De(6.22 g/m2)> Ca(6.21 g/m2)> Om(0.97 ind/m2)> Ph(0.01 g/m2).The species quantity,average density and average biomass of all feeding functional groups are highest in spring.Both the annual analysis and seasonal analysis show that the Pl is dominates in density and biomass of feeding functional group.Compare with the historical data of Daya Bay in 2013,the major dominant functional groups evolve into Pl of Timoclea scabra and Turritella bacillum from the De of Listriolobus brevirostris,Pl of Paphia undulate,Timoclea scabra and Vepricardium coronatum.(6)There are differences in the environmental factors that mainly affect the structure of macrobenthos community,secondary productivity and feeding functional group under different time scales.The annual changes are mainly affected by depth and temperature of water.The seasonal changes are mainly affected by depth of water,chlorophyll a,total organic carbon,sulfide,total nitrogen,total phosphorus,median particle size and sand content.The major affecting factors of annual changes are total organic carbon,median particle size and sand content.There are differences in the interaction between biological functional group or feeding functional group and environmental factors.The analysis shows that the biomass of macrobenthos in Daya Bay and the secondary productivity will change with the increase of water depth.Eutrophication maybe one of the major reasons that cause the dominant species of macrobenthos community gradually evolve into Polychaeta from Mollusca and Crustacea,the decline of species diversity and secondary productivity,the eutrophication impels the feeding functional of macrobenthos experiences the transformation from the coexist of various feeding functional groups to Pl,the structure of feeding functional group tends to simplify.The sediment is one of the major reasons that affect the distribution of macrobenthos,compare with the high silt content and clay content,the species diversity and secondary productivity of macrobenthos are higher in the sediment with high sand content in Daya Bay. |
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