The Communities Response Of Macrobenthos To Huge Engineering And The Ecological Restoration In Yangtze Estuarine, China

This paper first comprehensively summarized the master estuary benthos characteristics and put out AMBI index list of the Yangtze estuary benthos.Moreover, based on 25 surveys about benthos(intertidal and subtidal)from Feb.,2001 to Aug., 2006 and relatively historical data in the Yangtze Estuary(N30°10′～32°00′; E121°00′～122°50′),this paper did a analysis on benthos ecological characters and filled up the blank of study on the estuary benthos in China.The intertidal benthos was normally collected by benthos crab,while subtidal benthos collected by deep-water Agassiz trawl,benthos crab and so on.Totally,there were 1382 benthos samples collected.The paper includes four main parts,the first is summary on estuary benthos environment and its ecology characters;the second is study on the spatial and temporal changes of community structure of the subtidal benthos using some biostatistics methods;the third is study on the spatial and temporal changes of community structure of the intertidal benthos using some biostatistics methods;the forth is the research to Exergy and ABMI index characteristics of the benthos under the huge estuary engineering impact.The main conclusions follow:1.The community's response of macrobenthos to huge engineering in Yangtze Estuarine,China(1)Acipenser sinensis Gray is the first national class protection animal in China. It is a typical model of sea-river migration fish.It is a biggest kind of the individual in existing 27 kinds of sturgeons order in world fish,mainly distributing in the East China Sea,Yellow sea and the Yangtze River in China.Mostly,Acipenser sinensis lives in the ocean.From June to August,the mature individual arrives at Changjiang Estuary for procreation migration.In September or October,it reaches Hubei Province along the Changjiang River and gets over the winter there.In October or November of the second year,Acipenser sinensis begins to spawn and returns to the ocean soon.In spring of the second year,young sturgeon arrives at Changjiang estuary from April to August.After September,the 30cm-long young sturgeon goes into the ocean successively.Based on the macrobenthos taken in 15 stations from May,2004 to February 2005(Yearâ… )and from August,2005 to May,2006(Yearâ…¡)in Nature Reserve of juvenile Chinese sturgeon Acipenser sinensis,the species composition, biomass and abundance were obtained.Analysis on species composition,biomass, inhabit density;species dominance and community diversity were discussed.15 species occurred in infauna and the dominance species obviously changes as the seasons going.The biomass and inhabit density of infauna were 1.44±0.21 g/m² and 11.33±0.43 ind/m² separately.The community index,infauna community is instable. Epifauna has 59 species.The biomass and inhabit density of infauna declined from the first year to the second.As the seasons and years going by,species changes a lot and the dominance species have greatly difference.Epifauna community diversity is relatively rich and the community is more stable as the comparison to infauna.The parr of Acipenser sinensis is very frangible.Because of the degradation of water environment in Changjiang estuary,especially for the eutrophication and the water pollution,quantification research on the bait resource for the parr is extremely important.The seasonal change of infauna and epifauna biomass has unbalanced characteristics.(2)As a living place of various fishes,shrimps,crabs and parrs and famous for the Zhoushan Fishing Ground,the Hangzhou Bay ecosystem has the typical flimsiness and complexities.In recent years,a series of ocean engineerings started at Hangzhou Bay and were put into use.Benthos has the direct or the indirect relationship with ecosystem of Hangzhou Bay,in the field of most physics and chemistry processes.From 2001 to 2005,an oceanographic comprehensive survey of 20 sampling sites was carried out in waters around the area of Yangshan Islands in Hangzhou Bay(30°32′～30°50′N,121°53′～122°17′E)during the months of February, May and August,representing winter,spring and autumn respectively.The infauna and epifauna were the main survey contents.On the combination of Yangshan Harbor, the results are shown below.There were 31 species of infauna in the 3 years and the species number,biomass and the species diversity declined from 2003 to 2005. Species Shannon-Wiener indexes of infauna,from 2003 to 2005,were less than 1.00 and this indicated that the bottom of research area got polluted.The community of infauna presented simplification.By the comparison to the material in 1982,the biomass raised 2 to 4 times.In 4 years of 2001,2003,2004 and 2005,the total number of epifauna species is 77.Biomass presented rising in year 2003 and dropped later.There were 16 dominant species(Y≥0.02)and the succession of dominant species on the annual was obvious.Species Shannon-Wiener index slightly declined from 2001 to 2005(no survey in year 2002).The disturbance of the Yangshan engineering made the benthos habitat into fragmentation and the stabilization of benthos community structure descended.From the PCA analysis,the eipbenthos community differentiation of the 2003 to 2005 community got a lot change comparing with the 2001 condition.(3)An oceanographic comprehensive intertidal survey was carried out in waters around the area of Yangshan Islands in Hangzhou Bay(30°32′～30°50′N,121°53′～122°17′E)during the months of August from 2003 to 2005.As comparison of the synchronization material in years of 2003 and 2005,analysis on species composition,biomass,inhabit density,species dominance and community diversity are discussed.33 species occurred in infauna and the dominance species obviously changes as the years going by.From the community index and the community cluster, MDS analysis,infauna community is instable.As the years going by,species changes a lot,especially;the dominance species have greatly difference.From the community analysis,we found the communities of Northeast Yangshan Islands Section are the most stable and the West East China Sea Bridge Section was the most unstable one.(4)In February,May and August of 2001,the Exergy value of epifauna went up while, in 2003,the Exergy value from February,May to August went down under the ocean engineering condintion.In the two years of 2005 and 2006,Exergy of August got the highest value in the year.Among the five years,the Exergy change compositor was year 2003(104.0 J/m²)＞year 2004(47.8 J/m²)＞year 2001(41.8 J/m²)＞year 2006 (35.7 J/m²)＞year 2005(25.6 J/m²)(ANOVA,P＜0.01).The st-exergy of epifuana declined from 2001(352)to 2005(316)(ANOVA,P＜0.05).(5)From February 2003 to February 2005,the AMBI index of low water period had significant correlation to the suspended substance concentration,Shannon-wiener index(H')and the abundance index of the bottom environment.As the suspended substance concentration was 800mg/m³,the infauna benthos AMBI would be affected and would reach the maximum when the suspended substance concentration was 1460mg/m³.From August 2003 to August 2005,the AMBI index of high water period had negative significant correlation to the biomass,density,Shannon-wiener index (H')and the abundance index of the bottom environment.As the infauna biomass was 5.00g/m²,the infauna benthos AMBI would be fine and got no significant impact. When the infauna density reached 26.00 ind/m² and the H'value was 0.45 or the abundance was 1.75ind/m²,the infauna community could be in fine state while the infauna benthos AMBI index was close to zero.From February 2003 to February 2005,the AMBI index of low water period presented increasing tendency(ANOVA,P ＜0.05).The AMBI classification showed that some areas showed a transitional to polluted benthic community health,dominated by EG V while the EGâ… disappeared. From August 2003 to August 2005,the AMBI index of high water period presented increasing tendency(ANOVA,P＜0.05).The AMBI classification showed t a transitional to polluted benthic community health,dominated by EGâ…¢andâ…¤while the EGâ… disappeared.Generally,the ecological group of the infauna had the transformation from the sensitive species to the first order opportunistic species.2.The ecological restoration in Yangtze estuaryA restoration experiment of benthos w as conducted on the newly built northern and southern guided dykes located at the Changjiang River estuary.Ten tons of benthos had been put in the N 6 region of northern guided dyke in M arch of 2002 and 5 tons of benthos(mainly Crassostrea sp.)were put on the intertidal zone of the northern and southern guided dykes with 10 000 m long in March of 2004.The mean biomass and mean density of putting benthos were 43.15 g·m^-2and 10.70ind·m^-2 respectively in 2004.The result showed that,15 months later,the benthos species reached 21 species,the biomass and density were 26489.43 g·m^-2and 3399.11ind·m^-2 respectively,Shannon-Wiener diversity index is 0.98 in the experiment zone. Compared with the background,the species number,biomass,density and diversity index increased 9.5 times,40.31 times,7.50 times and 3.08 times respectively. Among them,the biomass and density of Crassostrea sp.are 19328.84 g·m^-2and 918.67 ind·m^-2,increased 483.39 times and 140.47 times,respectively compared with putting biomass and density.3.Comparison between the biodiversity index,Exergy and the AMBI index of the benthos under huge estuary engineering,in Yangshan Deep-water HarborBiodiversity change of the benthos in Yangshan deep-water harbor.There were 31 species of infauna in the 3 years and the species number,biomass and the species diversity declined from 2003 to 2005.Species Shannon-Wiener indexes of infauna,from 2003 to 2005,were less than 1.00 and this indicated that the bottom of research area got polluted.The community of infauna presented simplification.By the comparison to the material in 1982,the biomass raised 2 to 4 times.In 4 years of 2001,2003,2004 and 2005,the total number of epifauna species is 77.Biomass presented rising in year 2003 and dropped later.There were 16 dominant species(Y≥0.02)and the succession of dominant species on the annual was obvious.Species Shannon-Wiener index slightly declined from 2001 to 2005(no survey in year 2002).The disturbance of the Yangshan engineering made the benthos habitat into fragmentation and the stabilization of benthos community structure descended.Change of the Exergy in Yangshan deep-water harbor.From year 2003 to 2006,the Exergy of infauna declined(ANOVA,P＜0.05)and,from 2001 to 2006,the Exergy of epifauna got the tendency that went up in 2003 and then went down from year 2003 to 2006.By the comparison between the results of year 2001 and year from 2003 to 2006,the difference was significant(ANOVA,P＜0.01).This indicated that the infauna Exergy declined during the huge estuary engineering while the epifauna Exergy rose in the first engineering year and declined from the high point. Exergy can be used as a good way to estimate the benthos sub-ecosystem long term evolvement.AMBI change in Yangshan deep-water harbor.AMBI index gets the result from the species distribution on the ecological group(EG).In Feb. and Aug.from year 2003 to 2005,the AMBI index of infauna went up and this could get the indication that the infauna received heavily disturbance or polluted.From the analysis,the suspended solid is one of the main reasons for the infauna ecology succession,especially in Feb. from year 2003 to 2005.